You need a double pull, double throw (dpdt) switch and if you want it to function as an on/off switch too you need one with an off center. [link=http://www.radioshack.com/product/index.jsp?productId=2062530&cp=&sr=1&origkw=dpdt&k w=dpdt&parentPage=search]Heres a radioshack one.[/link] The black dots in the pic are the switch terminals.