I forgot to say that I'd be fairly surprised if there were something wrong with the controller on that bike. It might be an idea to test it before doing anything. All you need is a multimeter and about 5 minutes work. What are the symptoms? "Stopped working" doesn't give any clues to what's actually wrong. Another reason to test the controller is that the fault might be elsewhere that causes your new controller to fail, so it would be good to know what's wrong.
Also, the circumstances at the time of failure would be useful. Did the motor run intermittently, make a grinding noise, conk out while riding, or did the controller do the impossible and destroy itself in a warm dry garage while you slept, like most seem to do on this forum?