THIS IS NOT TESTED - but I pulled the dimensions from a holder that did work just fine (https://www.thingiverse.com/thing:3573956).
These were designed for a GoPro 3 through 7 battery.
Several of these holders also have places to hold 4 microSD cards, and there are built in clips to retain the SD cards.
I don't have a GoPro (and probably won't since I have a very LoPro lifestyle), but thought I'd post this here in case somebody a bit more adventurous wants to give it a try. I pulled the dimensions for these off a holder which I did confirm works with a battery, but I have not printed these. I have no reason to think they will not work since all the components of these designs (the SD clips, belt clip, inside dimensions and supports), have been confirmed separately in the double battery holder linked above. These are pretty much a cut and paste franken-holder of my other confirmed working designs. Still will leave these as a work in progress, so if you print one feedback is appreciated.
The STEP files will also be included for folks that want to make their own mods to the design (please post them as remixes though so everyone can enjoy it).
If you want a holder that holds two batteries (but not side by side), see the model linked below:
Parts are not oriented for printing, so rotate them 90 degrees and should be good. There is a built in support so no supports should be needed. I printed in PLA with 0.2mm layer height. I recommend using a higher infill like 40%, with "connect infill lines" in Cura, with 2 walls (2 walls is probably going to be stronger than 3 due to the thin walls.