Dave,
Hi-Spec in the UK make a nice rear caliper with integrated handbrake, it's UK IVA/MoT compliant so has to hold on a rolling road.
For the Group4 to be vintage legal, I had the original spec rotors shipped from the UK and yes shipping was as much as the rotors! If you ever need anything from the US, we have a Summit Racing store across town, just drop me a PM.