It's an easy enough part to replace, but does anyone know where to get a proper replacement from?

Hi, All, I've been fiddling with PETs lately and have found to my dismay that my original c. 1978 C2N just doesn't push the tape along as fast as it should. I opened it up, cleaned some minor funk out of the innards, but the old drive belt is just a little sloppy and has a kink on it where it sat around the motor pulley for a number of years between uses. The symptom is that FF and REW speeds are not uniform, there's no real "grab" when pulling on the belt or manually spinning different pulleys, and there is visible slackness in the belt. Loads are spotty, and they mostly fail. The "secret" trick of holding down the ">" key when the tape is moving does show that the CPU sees flux transitions, but it fails to recognize what's on the tape(s) as valid data most of the time. I know the tapes are good, and a slipping belt explains all the observed symptoms. It's an easy enough part to replace, but does anyone know where to get a proper replacement from? It's a continuous rubber belt, with a square cross-section just under 1mm on a side, probably about 250mm- 300mm long, give or take a bit (I didn't measure it). It looks entirely ordinary in the context of 1970s cassette transports. Thanks,