The attached .jpg is a solid model that I just created with my engineering software, showing what I was thinking of. This would be turned on a lathe from a peice of 2" round stock, and one face milled flat, then the cavity milled out. A bulb would be inserted thru the back side, and an amber lens glued or screwed into place in the front. The 2 ends which are turned to 3/4" dia would be butt welded into the headlight bar, after an equal length of headlight bar was removed.