..The 'brakes' are just the motor pulling against itself, so you'd need a stronger motor. You can find those virtually anywhere, and any selection of such has been exhaustively discussed before, I'm sure. Use the search function, it's a n00b's best friend.

Otherwise, the
shop has some quality parts, and more are coming in. XMODWorld.com and NewAgeMods.com both have shops, and there's always the off-chance that RadioShack themselves will actually have parts in stock, but don't hold your breath for that one.
Welcome aboard!