Cheap pilot lights under the bumper from autozone.
I got the same ones, cost like $15 or so

. I used a relay for the lights so that the reverse switch on the transmission doesn't burn out trying to pass too much current. The first pic explains the wiring, which was easy. For power, I tapped off a 12 gauge wire that I had run for my trailer socket adapter.
Mounting for these lights is pretty standard, so I just welded a 1.5"x5"x1/8" tab onto my bumper. I recessed them into the tube work fairly well, so I don't expect they'll ever break.
It's like having a set of headlights behind me when I throw it into reverse + with the lower mounting I don't get blinded by them if I leave 'em on to set up camp (personally don't like any lights at or above eye level)