Tape Speed and Replacement Belt??

[chuck]

I am trying to use an old, old Toshiba cassette deck
to save some tapes onto CDs. The drive belt is gone, shot,
mush, gooey masses of crud, and I have been unable to find
a replacement belt. Even the local audio repair shop will
not take my dinero. I have found a rubber O ring that fits
tightly, but with very little flex. Seems to drive without
slipping, but the tapes sound just a tad slow, kinda
draggy (played thru the sound card). Probably it's because
I don't have the Official Replacement Belt, but is there a chance
it's something else? Is there an adjustment, like a potentiometer
on the board, that helps fine-tune the speed? Or is it just a matter
of the mechanical aspects of the drive?

thanks for any help,

chuck