Found this thread on another forum:

Seems to indicate the Audi 100 pump (e.g. this one from eBay - is a valid replacement that just has a little bit less power assist.

two questions:

1) anyone know if this works or am I being stupid trying to save a couple hundred bucks?

2) anyone know offhand how many bolts i need to replace on the pump if I want to go ahead and replace the hardware while it's being replaced? (M8 X 35mm) Reading the bentley pages online it looks like 6 but wanted to ask