Just a simple spool holder for any printer with a 20/20 aluminium extrusion frame. You'll need a M8 bolt at least 30 mm long, a couple of M8 nuts and a 608 bearing.
It does not have a filament retainer, but I didn't find it to be a problem.
There's also a clamp if you need one to hold the cables.
EDIT: changed the holders' .stl because there was a slight concavity.
EDIT: Added another base with ledges to improve stability.
EDIT: Added yet another base with taller ledges to keep spools stable as they get lighter with use.
EDIT: Added a stackable addition to the previous base to use spools with a 50+ diameter hole.