Yes. Officially, the ruble was not allowed to leave the Soviet Union, and exchange within was tightly controlled, but this wasn't a huge issue, as there was a healthy black market and rubles were not hard to come by. In her memoir about visiting the Moscow in the 1960s, Sheila Fitzpatrick recalled that "every third Russian [on Nevsky Prospect] wants to sell roubles or buy clothes, chewing-gum, ball-point pens". Disregard for official policy and a desire for foreign currency - which had much more buying power on the black market - or foreign items hard to find in the USSR, meant that it wouldn't have been particularly complicated to get a hold of rubles in small to medium quantities simply by walking through a Soviet marketplace. Larger amounts too wouldn't be impossible to accumulate as even the privileged elite participated in black market transactions. Although there was an official exchange rate, Western money and goods could often be 'converted' to rubles at a hefty boost.

In the 1980s, when the best numbers are available, a dollar was worth 0.69 rubles, but would buy you 3 rubles in a black market trade. If you had in-demand items, you could get an even better return, with a $10 pair of new jeans fetching 50 rubles in Moscow, and 70 in Leningrad! Especially by the reforms of mid-80s, someone knowing what they were doing could quite easily accumulate a very large amount of rubles if they so desired. In any case, for the kind of day-to-day spending that an agent might need access to within the USSR, there was really no expected complications in accumulating that level of spending rubles.

It ought to be noted though that payment for American assets located in the Soviet Union wouldn't be paid for their services only in rubles. Large payments in rubles was considered a heavy risk, as an asset who had been turned and was operating in place would have little to spend the money on without raising eyebrows. As such, handlers of assets within the Soviet Union tried to limit how much money the Soviet citizen might be receiving for their services. A large bulk of the money they received was essentially held for them in accounts that they would, following the end of their usefulness and subsequent exfiltration, have access to in the West, but it wasn't always possible of course.

A.G. Tolkachev would be one such example of this. Earning only a meager 350 rubles per month in the radar design bureau, he received moderate amounts of rubles in the first few meetings, but for the larger future payments, which were to reach into six figures, his handlers wanted to place the money in an account in the West for him, an approach which he was rather uninterested in at first initially believing that he would never need to exfiltrate from the USSR, apparently continuing on undetected until retirement. As such, his first large payment was made in rubles, some 150,000 or so which equaled roughly $46,000 in value. In this case, with such a large amount needed, the above black market was obviously not adequate, and although no real details are given, we do know at least that the rubles were attained through a Swiss bank, not unsurprising given the Swiss' access to world markets in a way few other countries could do (and unsurprising that more on the specifics would be unknown).

The irony is that upon receipt, Tolkachev admitted that he had no use for the money and would just be hiding it! The importance of being physically given the cash - the equivalent of literally decades of work at his salary - was more psychological than monetary for him, a gesture from the CIA to show that they valued him and what he was providing. Although the CIA would continue to provide cash at times, as well as Western goods, it was comparative chump-change to the amount that began to accumulate in the account set up for him by the CIA, where he was paid $300,000 per year plus accumulated interest (which would have been roughly 1 million rubles per year). The latter would generally be what he had given over to him in cash form, and after the initial large payment where he had expressed disinterest in using the money, he would later explain the desire (along side the recognition that exfiltration would perhaps be necessary one day) as:

It happens that our exit is not being organized for today or tomorrow. During this time, anything can happen which can delay my exit or make it impossible altogether, for example I can have a car accident or become seriously ill and after that lose my ability to work. [...] [Something] unforeseen [could make it] impossible for me to get out of the USSR.

Tolkachev also expressed in communications with the CIA that he might use some of the rubles to bribe some of his colleagues in the Design Bureau, but the CIA was rightly aghast at such an idea which could easily backfire, and instructed him to desist from attempting it. Although they had given him considerable sums of money, the CIA believed him to not be behaving dangerously for it as:

Lavish spending does not seem to accord with what we know of Tolkachev's character and conservative lifestyle, or with his statements from time to time that he viewed the money we gave him as a nest egg, or insurance against adversity.

In any case, Tolkachev demonstrates several competing matters here. The need for something tangible by the asset obviously could be a strong one. It is not the same to 'know' that there is a large amount of money in your name somewhere in the distance which you can't access, as it is to have something physically of value, and it was hardly unique with assets for this to be the case. Rubles were considered high risk, but there was a necessary balance that had to be struck to keep the asset both safe and happy. Alternatives such as high value goods could be used also, alone or in conjunction (as in the case of Tolkachev), as well a valuable stones (which were offered to Tolkachev), which while suspicious are at least easier to keep hidden and in practical terms not much less useless than excessive rubles were.

In the end, it wasn't exactly suspicious amounts of cash that scuttled Tolkachev's operation, although it didn't help. He was likely put on the KGB's radar by Edward Lee Howard, a disgruntled former CIA agent, and subsequently a handler, Paul Stombaugh, was picked up by the KGB while planning a meeting. His person did include a bundle of ruble notes which were suspicious enough in of themselves but didn't tip the hand nearly in the same way that several messages, including one handwritten by Tolkachev did. Coupled with information from the noted mole Alderich Ames, Tolkachev was arrested and subsequently executed, never able to access the bulk of what he was paid, although the large stash of rubles he had accumulated did nothing for his case of course. His wife, who spent several years in the gulag did attempt to reach out to the US embassy for assistance, but was turned away due to them not knowing who she was, and she would die a year later, in 1991, of cancer. Although he had a son, Oleg, I can't find mention whether he was ever granted access to the account.

Anyways though, this has gotten expansive beyond the actual topic at hand, although I hope it is illustrative of some of the issues of payment! In any case, so wrap things up, the core take away should be that whatever the official policy by the Soviets regarding the inconvertability of the ruble, it was never particularly hard to get ones hands on. The thriving black market ensured that rubles were always readily available at hand, especially in the latter days of the Cold War, and even larger amounts could be gained through certain channels, although details aren't always going to be forthcoming. There is a great deal on the Soviet assets in America getting paid - not that dollars were in any way hard to get - but the CIA seems like it hasn't gone and published just who and how the Swiss banker was that got them rubles for Tolkachev, for instance, although certainly such channels existed in the international market if you needed beyond the smaller amounts available on the street, basically just a black market on a larger scale.

Bremmer, Ian & Raymond Taras. "The Black Marketeers Under Perestroika" in Soviet Social Reality in the Mirror of Glasnost, ed. Jim Riordan. Springer, 1992. 72-94.

Fitzpatrick, Sheila. A Spy in the Archives: A Memoir of Cold War Russia. I.B. Tauris, 2013.

Hoffman, David E. The Billion Dollar Spy: A True Story of Cold War Espionage and Betrayal. Doubleday, 2015.