Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2787032.

Clamp for mounting Ø56mm. Bolt pattern is Ø6mm and a 73mm square, center/center spacing.

Lower half makes up a little more than 50% of the diamter so it snaps on. There is a 1mm cutout between the parts to allow plenty of clamping force.