There actually exists a pretty long tradition of public shows that used trained bears in Russia.
Here, for example, is a painting done sometime in the last decade of the 19th century depicting a bear "show" (in this case a fight) by a Russo-Ukrainian painter Mykola (Nikolai) Samokysh. The bear trainers were a specific profession, sort of one of sub-sets of Russian harlequins (called skomorokhs), and the shows themselves most often were either fights (either bear vs bear, or man vs bear), bear baiting (either with hounds, or other bears), and comedy (the closest thing to the traditional circus). The comedy bears were mostly the ones that were born in captivity or semi-captivity and trained (some were blinded and de-clawed) for the purpose, while for the other types wild or semi-wild (that is, born in the wild, but trained since young age) bears were used.
This tradition was evidently popular enough in Russia and didn't really subside until the second half of the 19th century (Pushkin, for example, was one of the Russian writers to mention it in some of his works).
We know that the tradition existed as early as mid-1500s at the least, and the comedies in particular were known to be practiced at least since the 1600s, but most likely earlier.
Some circuses in Russia still use trained bears as part of their shows (including the unicycle), although it is not quite the same thing as the traditional bear shows, which were largely outlawed by the 1860s, although they took until the first two decades of the the 20th century to die out completely. They mostly use bears from zoos and have been locking horns with the animal rights activists more and more in the last few decades.
I can't find any sources in English I'm afraid, but there is some scholarship in Russian.
Royal Hunts in Rus' (3 tomes, written between 1896 and 1900). - the only source I could find that was available online (no translation, as far as I know).
