I couldn't find a version of this anywhere else online, so I thought I'd make one! This is a 1x1 holder designed for gridfinity. The battery just fits in that size, but the walls are a little small on the sides. From my testing this hasn't been an issue, but might be if you're putting extra stress on that. This also does not have a rim for a lid or for stacking as there is just slightly too little room for it.

I've purposefully designed this to be slightly loose so that it should work regardless of how well tuned your printer is. I printed this on both a P1S and an Ender 3 and it worked with both. I've also added the Fusion 360 file if anyone wants to make their own tweaks to the design.