I had the same dilemma. Take the bulb housing out of the casing and drill a hole in it. Use a sheet metal screw and attach a terminal connection to it and run the wire out with your positive wire, now you have a ground.what I got from the person who sold them to me, he said I just needed to get H3 12v lights so I bought some cheap LED H3 12v bulbs to test out but like you said, there is only one wire. How can I wire that if there is no ground?