Summary

Based on right part I3-M08 (right one if you're facing your printer), I designed this thing to be secured on top of the z-top mount with M3*30 screws. Then using a 6 or 8mm threaded rod, some nuts and a spacer to support the filament spool.
I was afraid the threaded rod could bent, or the printer to lose his balance slightly, but no, not happening.