Digitrax makes rhe AR-1. It list for about $30 I think. I have 1 on my turntable pit rail that works OK I know several other companies offer them. I would recommend the Digitrax though. you can also use a Double Pole Double Throw switch-DPDT. With the two wires from the source to the top two poles and the bottom two wires from the same source crossed to the bottom two poles. Hope this helps. Tweet.