RC switches are not very common. But the cheapest one I know off, the Turnigy switch is very fragile if it comes to voltage.
http://www.hobbyking.com/hobbyking/s...Search=Turnigy switch

The battleswitch you can buy at Technobots or Robot Marketplace is not as cheap.
http://www.technobotsonline.com/batt...relay-10a.html