Summary

This one is mainly for the selfie-stick people, but if you ever find a reason to GoPro mount a bottle to something else it'll work for that too.

I've printed from TPU. Cap scaled .2 mm for a tighter fit. Inner 3.5mm brim and painted on supports at the bottom tip of the lower prongs recommended for print stability.
I had issues with dome overhangs at low nozzle temps, watch out for that.