I needed several spool holders and I couldn't find anything quite right for me, so I created this attractive, super simple, yet surprisingly sturdy spool holder that is entirely 3D printed and snaps together. It is designed to fit almost all filament spools up to 1 kg (limited by size, not weight)
I printed at 3 shells and 20% infill, but that was overkill. You're probably ok at 2 shells and 10% infill (let me know in the comments!)
The top rests on the holder for easy spool removal, and the bottom legs snap into place to hold the sides together. Depending on the accuracy of your printer you may have to use an adhesive, but I got a perfect fit.
Print 2 of the sides, 2 of the legs, and 1 of the top.