I was in the same boat as you are, looked everywhere for one but I could not locate one. Over a year ago I posted in the Fadal Facebook group and guy in England ask me if I was still interested and bought it from him, I got lucky.
If I was you I start installing it with the MI12 and MI8-4 and get it done chances of finding a 1570 are slim.
Check this page https://www.doovsprojects.com/projects/adding-a-renishaw-probe-system-to-my-fadal-vmc that fellow did a wonderful job there is schematics and clear instructions.