I have been making to make this bearing spool holder since I purchased my K1 max.
Its more hardware intensive but produces a simpler design in appearance.
Probably could have made it with less. I had the hardware on hand in a holder for my ender 3.

You can use either M8 or 5/6” hardware.
You will need a
122-125mm threaded rod
2 Nuts
1 Nylon lock Nut
2 608 Bearings

I’m not giving an exact length for the threaded rod. If you use M8 or 5/56” you likely need a slightly different length. The standard nuts are different thicknesses. M8 being the thicker. If the rod is too short the Lock Nut might not fully engage. Too long the cap might not fit on. Error on the long side. The end cap is purely for appearance.
That being said 122mm works well with 5/16” hardware.