I'm currently using this part to mount my Bontrager Ion 200 RT light to a Blendr GoPro-style mount on my Trek bicycle.
I initially printed this with a 0.4mm nozzle (see red part in the photos) and it worked OK, but the latch wasn't as secure as I would have liked. I switched to a 0.2mm nozzle (gray part) and it snaps in very securely. It all comes down to the latch feature (circled in red) - it needs to be sharp enough to catch the mating edge on the light.
Note: you can print this with a 0.4mm nozzle and get a sharp edge by using a file or some 320 grit sandpaper wrapped around a sharp corner. This is a good alternative if you don't have a 0.2 or don't feel like swapping nozzles
Material choice is up to you, but I'd suggest a PETG, ASA or something that will hold up well outdoors.
Per the attached images, you'll need to orient the STL model as shown (to maximize strength of the latch) and print with supports. Unfortunately the part is too complex to print without them, so I went whole-hog and used supports about everywhere. At least on my Bambu X1C the supports worked really well and were easy to remove.
Feel free to ask questions or post your build. I built this as a parametric CAD model so it's easy to make adjustments if anyone has any unique configuration requests. Enjoy!
Edit 3-28-24: Added a second version with a longer (+ .25") arm to better fit my new bike
The author marked this model as their own original creation.