I made this up for my select plus, as its home has a low slanted ceiling and otherwise would not fit. With a standard size spool, the extruder will just clear when using the maximum print area.
You may want to add a binder clip to the rear to keep it from racking a bit on full spools.
I just printed in PLA, and its plenty strong.
This will mount up to the screws that hold on the stock filament holder, so no modifications are required.
Monoprice Maker Select Plus
Print it on its "back" and it'll print fine without supports.