That's pretty weird that you post this up now...I was just contemplating making some of these the other day, I actually talked with the wifey about it...
I was thinking about forming a fiberglass housing that would replace your original. The housing would hold the light so it would only protrude about an inch or so...it would fit a 6" or 4" but would include a formed area for the light to mount into but still allow the light to swivel in all four directions for aiming. then you would have to disassemble your original and use the lower mounting part, the mirror and mechanism and the wiring would all route together like OEM.
Or I could make one that would snap on to the original mirror, but it would have to stick out a little more. and you would have to drill a hole in the mirror housing for the wires.
something like this terrible paint tragedy