Hey Steven -
Radio Shack will have what you need. Electrical folks on the Forum correct me: I think DPDT (Double-throw/Double-pole) will work, but you may only need SPDT (Single-pole...) It depends on how many wires your current switch has. If you're only controlling one wire (positive or negative), that's single pole. There will be three connections on the switch. The source comes in and the other two wires that go to the motor are hooked up to the other poles on the switch. When the switch is in one position, current flows to that wire. The other switch position sends current to the other wire.