I took an old spare socket and cut a slice in it with an angle grinder with a cut-off wheel.
Works like a charm.

Just like my oxygen sensor sockets I have at work. The slice would work great as long as the need for Super Torque is not required.

It's a driving light...surper torque isn't required on these.....I have the same light bar as the original poster.
Deep well socket with a hex top turned by a combo wrench. Cut the wire and pass it through the center of the socket. Reconnect the wire, use solder and use shrink tube.
Actually, that's a viable idea, but with my method of cutting a slice in an old socket, there's no need to cut or splice any wiring. You can't make a complete revolution with the socket, but you don't need to make many to tighten that nut. Just take the socket off and slide the wires back in and tighten some more.