Ah, I begin to see the problem. Reading up on these it looks like they have a rim drive arrangement on the reels and no capstan. That means that the tape speed is going to change from one end of the reel to the other, which is not how normal recorders work. That could be corrected digitally, though it would largely be guesswork as to the rate of change. Alternatively, it might be feasible to lace the tape up on a conventional machine in such a way as to bypass the capstan.
Otherwise, you would have to find a compatible machine on ebay or fix this one, and to be honest this design is weird enough that I'm not sure where to start. If the motor is truly stuck, e.g. it's not just an idler wheel turned to mush, it's probably going to need to be disassembled and that's not something I can really advise on. Good luck with it, though.