This guy has [link=http://cgi.ebay.com/Pittman-19-1-VDC-19-5-1-Gear-Ratio-Electric-Motor_W0QQitemZ7593035961QQcategoryZ71400QQrdZ1QQc mdZViewItem]10 pittman 19v motors that might work. And at $5 bucks a piece.[/link] They might work.
I don't know about the "reserve" price though.

This auction has two for 5 bucks, no reserve, but you will be battling one other bidder.
[link=http://cgi.ebay.com/TWO-PITTMAN-DC-ELECTRIC-MOTORS-19-1-VDC-MOTOR_W0QQitemZ7593259252QQcategoryZ71400QQrdZ1QQc mdZViewItem]Two pittman 19v motors bids starting at $5[/link]

I use a pair 14 volt pittmans on a 12v battery, and the boat is way over scale speed.
Just take the gear head off of these 19v and see how they run direct drive.