This is another cable wedge for extension cords and your average filament spools. I had trouble getting the the other ones to fit and not crack, so this is simplified and a bit more robust.

Just print two of the these and drill a hole into your spool with a spade bit (I used a 1.5" / 37.5mm) bit.

There's two sizes 10mm and 15mm inner diameter (ID) for the cable thickness. The "3D Print Canada" spools I sized this to are about 54mm ID, and they fit nice and snug without glue. You can scale to fit other spool inner diameters.

If it's not quite tight, I'd suggest using hot glue to hold it together.