Made this to fit a brake light to my old Schwinns. sizing's not perfect and there's a little flex (it's just a hair too wide and the screw holes are tight for the ones that came with my light), but it clips on tightly and holds my light at the right angle to be seen by anyone behind me.
I printed them in ABS because that's what was loaded in my printer, ASA would probably be a better option for outdoor longevity. PLA and PETG would probably work as well, might deform depending on how hot your summers get though.
The author marked this model as their own original creation.