I needed a way to mount a laser to an L bracket for a lunchbox laser light show project (http://laserlunchbox.com/LunchboxLaser_08_kh.pdf). I designed it in OpenSCAD to fit the laser module I have, and to fit the 5/8" bracket I had. It's somewhat parametric though it has some issues when scaled outside the intended size. The mounting holes are teardrop shaped to facilitate printing, using a simplistic teardrop module I created (there are better teardrop modules on Thingiverse, but it is included for completeness). If the holes are an issue (they were for me), they can be commented out.

It's designed with a small slit and tabs which can be clamped together with a M3 bolt, nut, and a couple washers.

Print. Add bolt, nut, and washers. Attach to whatever you want.