I just bought a UForce 600 and was looking for a fix as well. It turns out that my bike (Canadian version) is already wired for a backup light with a 15amp fuse and relay, just no light. Just by the tail lights there is a yellow wire with a bullet connector that’s not connected to anything.
I connected my light to this wire and by golly it comes on when I am in reverse. Since there’s no room for an additional light on the back of the bed, I am mounting two small led lights above the rear window and routing the yellow wire to them.