Welcome to the Parallax Discussion Forums, sign-up to participate.
To turn it off, you could turn on another motor attached to the axle of the first one that you turn on, spinning in the opposite direction, which would let the module stand still while you turned it off. :-)
@RS_Jim: I had thought to add everything on that list except for the brushes and slip rings. What a great idea! This would increase the speed and diminish the wobble almost completely! Where would I buy these?