This is designed for a GoPro 3 through 7 battery, and has been tested with a battery (only had one, but tried it both slots, so should work just fine). I did not get a pic before I gave it away (I don't own a GoPro).
The case can hold 2 batteries and 4 microSD cards on the front. The MicroSD's are retained in the slots by clips. The pic attached to this thing is from a single battery holder but the design of the front is the same.
The STEP file 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).
The model is not oriented for printing, so rotate it 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.
If you want a single battery holder, I have them here: