or just go with a 914 rear disk and caliper:
http://www.pmbperformance.com/page/page/1925687.htm
Just look at that last picture of the 914 rear caliper: That stock mechanical handbrake lever is very cool.
Unfortunately the disk and caliper are not very large...but may be enough to convince our inspectors that the brakes are 'upgraded' to disks with mechanical handbrake