A number of people have contacted me with regards to the 3D building process to make one themselves :-
My best advice is only to be careful whilst printing the gear part.
.... its printed with a wall thickness of 0.4mm
as it makes a 0.4mm spline that fits into the slot of the feedback potentiomenter.
If your printer fails to make the spline then you can easily slot/melt in a thin metal vane. (no worries)
Its also a good idea to print the Leadscrew first to see how your printer deals with the overhangs involved (If they dont form neatly then reduce your Z steps to finer detail .....