I install about a dozen canopies a week at my work, we use a 3 prong plug
wire 1 - ground
wire 2 - we run to trucks park lights and to the canopy dome light ( so you dont forget to turn off the dome light and wear down the battery)
wire 3 - on a ranger has to go right to the brake switch, there is no chmsl wire in the truck like most trucks have.
any retail store that install's canopies should have wire harness's, 3rd brake lights, dome lights, light duty topper tape, and cap clamps. A few companies to check out would be API, ARE, Raider, Century, Action truck caps, leer ...
API is more into lights clamps and wireing, hope this helps