Needed one of these to go next to my printer, and since I had some low-quality ball bearings to use up, I designed this one. It works for most spool widths without adjusting width or anything.

The bearings I used are 5x10x4mm (MR105 I think) and the whole thing is held together by two 5.0 x 80 mm wood screws. I also used some 2.65mm diameter pins for alignment, but you can probably skip these.

FreeCAD source included for easier modding, If you don't have bearings this size, you can probably just make it a plastic-in-plastic bushing.