I picked up a set of 'tractor' lights at autozone for $15 a piece. their about 3 inches in diameter, 55 watt, and are a self contained unit. the housing is rubber with a built in mounting braket.
Something to keep in mind, factory wiring on any vehical is just enough to carry the load of the factory lights. DO NOT attempt to power your new back up lights using the factory harness. Instead, run a new line from the battery to feed the lights. then use the back up light wire on the harness as your switch.