In the comments of my other Ryboi Thing, lowlight was after an inverted version, to hold batteries or pehaps convert a Ryobi battery to suit other uses.
So here it is.
It is a bit lose, so if you want it firmer try scale 0.9-0.95ish, but too tight and it is useless.
The holder, if wall mounted, is at 90 degrees, this is because the bridging at an angle would be impossible. So I include a small 5 degree wedge, which you can glue/acetone to the holder so batteries won't drop off in a small quake. You will need to drill through the wedge.
I haven't got a need, but some appropriately bent metal tabs in the side slots could be used to get power from the battery to some wires.