Simple spool roller attachment for Ender 3 and others. It fits your existing spool holder, just need to drill two small holes to fix them in position. Superglue or epoxy could work as well.

You will need two small bearings R3ZZ or R3RS (3/16 ID x 1/2 OD x 3/16 Wide). The bearings are superglued onto the holders

I printed them with a 0.8mm nozzle, but your standard 0.4mm could work as well

Print 1 part as is and then another one mirrored if you want to screw them on and have the screw on the same side. If you are going to glue them on, then just print two as is.

Fits spools with a ID down to 46mm