These guys have sorted me out a couple of times in recent weeks.
1984 Porsche 944 caliper... not available from the usual suppliers unless you wanna spend £400 at dealer. New piston, seals and painted up and delivered back within 4 days £80 odd quid.
1967 Triumph Herald type 12 calipers (not available) both sorted and back within 3 days £89 inc vat and return delivery.
If you want custom paint job on the calipers they do that too.
Check out their website.
i sent a pair off to big red a couple of days ago, i know them by reputation so whilst they arent cheap, i know the calipers will be perfect when they come back so thats good value. ill ad a addendum to this when my calipers get back.