I've installed a pair of flood lights under the back-bumper of my truck. Currently I have one wired into the back-up light circuit, and the other is wired with a switch to a constant 12v source. I would like to wire them-up, so they both come-on with the b/u lights AND/OR can be switched-on from the constant 12v source. I guess that I'd need some-sort of relay for dual power sources to a single accessory, but I wouldn't begin to know where to find one. Anyone have a suggestion?