I use this for an airsoft gun, to mount a flashlight I bought at Costco (set of 3 for under $20). There are many other similar designs on Thingiverse, but I had trouble using some of the files for editing the design, so I just designed my own in Viacad.
The flashlight I used has a 29mm diameter, so standard 1-inch (25.4mm) scope rings would not work. 3D-printing to the rescue!
In case anyone wants to modify the design for their own lights, I have included the STEP file. I have never used STEP files, but Viacad can export them, so I hope it's useful. If not, there's not much I can do to help.
I printed it with 20% infill, but probably should have used more, though it feels plenty strong as-is.
Use 6-32 x 1/2" machine screws for the top clamp, and 6-32 x 1.25" machine screws for the mounting clamp.
I printed it in PLA, but ABS might be better for use outside on sunny days, when PLA can get a little soft. I'll just have to see how it goes.