A simple single / dual light mount which goes in place for your average 1 1/8" Ahead spacer on modern bikes.  There are several versions of this design including a rather expensive one you can buy. Simply melt a M5 or M6 threaded insert in the adapter and you are ready to mount your light. I also added a “light holder” which I found a bit to flexible even for smaller light. So I bend some 15x2 mm flat aluminum I had lying around. OpenSCAD files are included in case you want to modify anything.