Drawbot plotter base pen holder
by UechiMike, published
A quick and dirty union of the two part base (saves 3 screws!)
Unprinted and untested but should work just fine.
Put in use.
See the original thing for details. I don't think this is the pen holder you want to use - it looks as though this one is setup for penup/down but the weight and balance aren't quite right.