ONKYO TA-2570 cassette deck restoration & mods

It was fun to read your adventures tuning up that cassette deck; brought back some good memories. I always liked that Onkyo but never got one. Over the years, I've had a HK CD-301 but I really wanted 3 heads. I dumped it and got an Aiwa F-770 and much later, a Sony TCK-611S.
Where do you get "known" good belts these days? My F-770 is in need ..., I really should pull it out of storage and play with it ...