Tell us about yourself!
You could use an on-off-on switch with the two "ON"s cross connected so that essentially you're just switching the wires round. Because you pass through zero (i.e. the off position) no nasty things happen. I have done this for a friends 3ph AC motor to switch direction. I don't see why it shouldn't also work for DC.
RetroPie Arcade Cabinet (Cocktail Style)