This is a customizable spool holder for use with 608 bearings and an M8 threaded rod. You can customize this by using the Thingiverse Customizer or by downloading and changing the values in the .scad file (You can also use the method described in this thing.).
To make this fit your filament spool, measure the hole diameter with something like a caliper and change the value "inner diameter" to your measured size. As my prints tend to shrink slightly I added 0.2mm to the diameter for a perfect fit. Also, you can change the value "bearing fit" to "Tight", which is actually the exact outer diameter of the bearings, but again, it didn't fit in my case, so i made the "Normal" fit value slightly bigger. I would recommend to only use the "Tight" fit if your printer is really well adjusted, but even in this case you would probably have to sand the bearing hole to make the bearing fit. The third value changes the position of the bearing from the inside of the spool hole to the outside. I did not test this version, but it should work as fine as the inside version, although you will most likely need supports. With the outside version you could fix your spool with a washer and nut, if anyone tries this, please let me know how it worked out!
I only printed a pair so far, because I have mostly same sized spools, so please post your makes and let me know if anything doesn't work as intended, I'm happy to help!
I also attached the .stl file of my spool holders for 45mm bq spools as seen in the pictures.