Hi Wes,
I've been down this path - he's an edited extract from an earlier post of mine (2023), hope it helps..
I spoke to Nelson (based at Highfield Road, Camelford, Cornwall PL32 9RA) and they asked me to send the seals I had and they'd see what they could supply.
They were able to provide the hydraulic seals - the two for the air valve piston (both identical) and the two for the main bore. The part numbers they quoted on the invoice were S9429 (air valve x2) and S9450 and S9619 for the main bore piston.
There's another seal at the vacuum chamber end - it transpires its the same as the servo seal used in Mercedes servos (also Ate but a different model) and is also the same as the throttle body on the 600 - these came from Niemoller in Germany - I had to buy 4 of these as there was a minimum order, so I have 2 spares! Part number on my invoice is D 08 175, described as a B8x16 DIN6503 sealing ring
There is also a thin O ring that seals an aluminium plug at the end of the main bore, a fairly generic part I think. I didn't find a new seal for the vacuum chamber - I reused mine, but I guess there would be a source somewhere. Gasket is easily made from sheet material.
The hydraulic seals were very cheap - just a thought, but if you have other interested parties down under is it worth buying a job lot? The Mercedes one was the (relatively) expensive one.
I also bought some 2002 servos for parts, as i needed a replacement vacuum chamber (one of mine was dented) and kept a few spares from these, but from memory the hydraulic side of things uses different diameter pistons/seals.
I rebuilt the servos myself with re-sleeved bodies, and with everything else new or rebuilt, the brakes are excellent!