A Gridfinity Papermate Inkjoy Pen Organizer. Couldn't find one, so I made one. Thanks to Chof258 on Thangs for providing the template.
https://thangs.com/designer/chof258/3d-model/Gridfinity%20Template%20with%20fixed%20bottom-422524
Fits 36 InkJoy pens. I purchased a 22 pack and a 14 pack so it all worked out.
36 - 11mm holes in case you want to use for other brand pens. Enjoy!