I used a plate mounted plug purchased at autozone or something similar. A real standard design. Hung it below the hitch ball and tied it up with tie-wraps. Held well until I insisted on using the highway cut thru for a u-turn and the rear dipped enough to drag the bracket & plug a bit. Broke the tie-wraps but the connection held. I am now looking for a method that will allow me to do the round receptacle in a hole cut directly into the rear filler panel below the license plate. Not sure who makes it but I'll figure it out.