It took me about 20 years, but I finally found the correct Kenwood TH21-BT
With all of the accessories that I've found over the years, this allowed me to test each battery and radio and figure out which ones work and don't.
So I went and made an "unboxing video" and demonstration with all of the accessories that I've found over the years:
After I got the correct radio last year, I've started selling off the ones that weren't right. Which I think was about 7 radios?
Since then, I've also found some interesting pieces like factory replacement parts, covers, stickers, buttons, etc. I'll have to take photos/make an updated video of those soon.
If you ever find any of the shorty UHF antennas, I'd definitely would want some. At least 2 for my personal collection, and then maybe some extras so I can fit on the radios that I'm trying to sell that don't have antennas.