[Bob Steele]

You might try something like this:

http://www.ebay.com/itm/L-R-Motors-f...AOSwgApXAwd o

or this

http://www.ebay.com/itm/L-R-Motors-f...AOSwBahVDc6 E

These are wheel chair motors/gearboxes that should easily be able to be controlled by FIRST motor controllers.

Wheel chair motors are pretty robust and are often used in Battlebots. (Or at least they used to be used a lot.