I've rebuilt a set of AUDM rear calipers using parts from U13 ATTESA calipers.
The housings are different, but all the internals are the same. I think they used different size rotors, so the caliper housings had to be different.
Kits are available. From memory I got the seal kit from Slacks Creek Brake and Clutch for about $40.
When you're rebuilding them make sure there's no rust pitting at all on the pistons, or the seals won't last long at all. Rust was the reason I needed the ATTESA parts for mine.