1990 Mk3/4 camper, servo trouble

[Zombie camper]

I am trying to locate a brake servo for my mates 1990 transit campervan, the old one failed, motorfactors seem to think there are four possibilities, none of which is available, the owner bought one from ebay that was advertised as Mk3 but its totally different, the one I need has two M10 studs going through the bulkhead on 90mm centres at 45 degrees approx, and mounts the master cylinder on two M8 studs on 65mm centres horizontally.
The failed servo was full of engine oil! presumably from the vac pump so this may also need attention, does anyone have knowledge of similar problems, and suitable donor vehicles? Thanks in advance.