Are there any conventions, marketplaces, or swap-meets of note?
Hell, that ain't "retro", that's "modern". That's IBM-PC 16-bit (1980s!) for f's sake.
If you want 'retro' go back further to 8-bit (1970s CP/M!) or even 12-bit (1960s PDP-8!) or even (wait for it!) the 1950s!
Maybe more popular than beanie babies.
Maybe not.
[An aside: It's "Trash 80" for TRS 80. "C64" for the Commodore 64. TRS80's were great computers, but bro culture predates them. The C64 was a better computer for gaming, but not for business. You could get TRS-80 service from Tandy/Radio Shack. You could get tools for multi-user environments.]
Lots of resources on Youtube. Youtube Premium might be a good first purchase.
Good luck.