This is a simpler version of thing 3155344 which eliminates the ball bearings. This works better for me because it eliminates the spool 'runaway' due to the very low friction of the bearings.

Included are both STL and Fusion 360 design files. If you want to change the holder's length, change the net_length user parameter in the Fusion 360 design.

I used the STL model here on the left side of the printer but it should work on both side. If you want to make the support wall visible or non visible from the front, simply mirror the model in your slicer.

I printed it with PETG for its lower friction than PLA (?). Layer height 0.2mm, 25% infill, and no material support (rotate it in your slicer to lay on the support wall).