There are a couple of stores I used to go to that sell vinyl, but I haven’t been in a while. They never did much new stuff but they would sometimes surprise me. Both of these were close to Taipei Main Station.
This place always had some vinyl, but I haven’t been in years. It was very cheap stuff, some of it pretty weathered, but I found some pretty good stuff (again, this was years ago). The shop is on the second floor.
Looking at their site, it looks like they still sell vinyl.
There’s also a shop right here. This one’s downstairs and had a better selection, I thought.
There were a few others but I either can’t remember where they are or they’re gone now.