As I needed this for myself made a simple small model.
Simple Holder for 3D Pen. Tested ands fits perfectly to Crelando (Lidl Brand) 3D Pen.
Sizing of holder is:
Length - 50mm
Bottom inner Diameter - 18mm
Top Inner Diameter - 27mm
So you can check your device (no necessary 3D Pen) and if it is ok for those values you can use it.
Holder fits to the wall by two Hex pins. I was planning to make a screw fittings, but after checking this one I found there is no point for that.
One last thing. Holder have a little tilt (10 degrees) for easier operating.