the first link doesn't have cassette tape (or they ran out).I just repaired a tone arm for the owner of ATR Magnetics- she assured me that they do indeed have cassettes.
I'm working on a Nakamichi 700 'Tri-Tracer' right now; just for the record the machine uses a pair of idlers to run the fast wind functions. The correct tire replacement for these idlers is ST 937 (originally a PRB part number), available from Russell Industries, although I was also able to find them on ebay.