I made a remix of https://www.thingiverse.com/thing:3979065 to also facilitate spools which don't have a solid interior core to ride on the bearings (pic included as example). The particular brand of spools I use don't have a solid cylindrical core to ride on the bearings so I modified this design a bit to hold a 4th bearing towards the end to keep the spool from sliding off the bearings. In testing I don't think it's necessary to have anything on the opposite end as the spools tend to wander towards the far end of the spool holder. This 4th bearing does not inhibit putting the spool on the holder.

Uses 4 standard #608 bearings (22mm diameter, 8mm center hole, 7mm wide)

Requires 3x spool holder dowels (I print these at 100%. They are a tight fit but can be tapped in with a small tool/hammer).

I've included a picture showing the holder with bearings attached. I recommend installing the bearings in that order (A>B>C>D). If you install D first it can be a little difficult to get C seated.