I printed the spool Holder featuring Emmet's Gear bearing, when I realized I had a shelve hanging over my Kossel, so there wouldn't be space for the spool.
But since most of the upper middle part of the Tower is never used, I figured I can just place the spool there by tweaking the spool holder's mount.
after some iterations, here's the result. You need some M3 by 8 bolts and some M3 nuts for this to hold, although maybe not all holes have to be used.
I use this on a Kossel XL and have no way to test this on a smaller Kossel. Therefore please tell me If it works for that one too, so I can update this description.