I've uploaded the source files for this holder to Thingiverse here. Both the OpenSCAD and STL files are available and come in two versions - the short and extended. I've only printed the short version for myself, which is big enough to support the 1kg spools I've been buying. The extended version should be able to holder larger spools.
This is what the models for these looks like:
...and this is the holder as mounted on my printer box...
I've had to make some modification to my 3D Printer Box before I could make use of this filament spool holder. While making these changes I also moved the exhaust fan to the rear of the box (it used to be on top). I had to cut out a hole for the filament to fit through, a hole saw did the trick here, also left a mess...
I had a rod lying around which I've decided to use, this is actually for holding up plants, but works nicely here. The rod is metal but covered in plastic.
After everything is cleaned up, and a spool fitted, the printer is ready to go once again.