I've got three different sets of allen keys:

• Würth art. 0715 39 10
• Beta 96 BP/SP9
• No-name 7 keys

All of these holders are specifically made for each one of them and all use the same Multipoint attachment. I prefer the Bolt-Locked Multipoint, which requires a 9mm Small Thread T-Bolt and a snap, where I prefer the Weight Bearing Snap.

I printed these in PETG, but PLA should also be fine. Use 3 perimeters and 0.2mm layer height. Use brim and support on build plate.