It's a cap. The guy's guessing. I bet I could find the exact part at Digikey if I took the time to do so.... but...

Discreet fuses are never placed on RC motors.... ( it's easier and cheaper to put in a fusible link if someone even thinks to use one... ).

Capacitors are all but mandatory.

They are used to lower the amount of RF noise generated by brushed motors

Look for replacement capacitors on Tower's site or any other that sells brushed RC motors.