For example, how they sold the NES, SNES, and PS1 minis in retail stores, how gamestop has classic-ish stuff like Digimon digi pets and Disney afternoon toys. Even rereleases of Tamagotchis and Tiger Electronics. But what did the 90s have for "Nostalgic adults"? Any kind of rereleases?
To answer that would ba a long list of examples in many different forms of media.
I don't want to drift into an examples list, as that is not wanted, the way I understand the rules. But maybe it is helpful to point towards common theories on how nostalgia develops.
The most common theory of nostalgia are the so called x - years - cycles. Very prevalent is the 30-years-cycle, but there are other cycles that come up in the description of nostalgia (40-yeas, 20-years, 15-years ...). The reasoning behind it is, that people who create media will be influenced by things that were popular during their formative years, and then the question is, what are those. Childhood and teenager years are often considered most influential in that regard, so you take the time it takes for a generation of children or a teenagers to reach a position, were they are the prevalent force to govern the taste of the mainstream, and that time frame is then the base for a x-year-cycle.
It is almost always possible to come up with examples to 'prove' the existence of a certain cycle. Especially because most things in culture can not be pinpoint to a definite timestamp.
If you go with the 30- year - cycle theory you'd search for and find 90s nostalgia for the 60s:
Mission Impossible reviving a TV-show that ran in the 60s and 70s,
Austin Powers taping into a hippy nostalgia,
Arguably the 'oldies' rock and radio stations concentrating on it really flourished
(...) but as I said to go on here would end up just being a list of examples, that can be easily googled.