I couldn't find a Gridfinity compatible 1/4inch Router Bit holder so I made my own. It fits in a 5x2 space (such as the default Gridfinity Rugged Box) and is angled so that bits don't take up more than 1 unit in height.

This was printed in PETG and is meant to be tight so bits don't move around - after a few uses of each hole though they should be pretty comfortable to place and remove. Because PLA has less flex the hole may be too tight.

* Let me know if you would like versions with less width or different hole tolerances.