Kossel K800 proximity sensor bracket

This is yet another bracket for a proximity sensor (12mm diameter) as I was not completely happy with the design I found.
I made this bracket to fit the K800 magnetic effector, more specifically for "Kossel k800 Centre Block & effector 12mm - 13mm" from drtaly (itself a remix of "Kossel k800 Centre Block & effector" from Weeper), but it will fit other effectors of similar shape like kikuon K800 Effector V2 (https://www.thingiverse.com/thing:829446)

I was after a bracket that was easy to inst