Per Rick, the motors are thermally protected for a reason. The motor engineers decided operating past that point was bad for the motors. You're shortening their life if you're running them that hard. It is, of course, up to you to decide if it will still survive the competition season despite this. Extra cooling is certainly a good idea. If you could modify the banebot trannies to get some airflow through the front vents of the FP, then it'd help. You could also consider changing your gearing slightly to push the motors less.
If you choose to ignore all this advice and get an unprotected motor,
this 2005 thread has information about ordering the motors. I'd order a some spares if you go this route.