A collection of 3D files for the Monome Arc Clone by Johannes Neumann, which can be found at https://github.com/TheSlowGrowth/MonomeArcClone/
Knob - D-Shaft knob, fitment can be difficult based on the accuracy of your printer and material used.
Light Shaper - I've printed one of these but haven't tested fitment yet. You may need to use a raft to print successfully.
Case - I haven't tested this one yet, it is too large to print on my Ender 3.