I've just been upgrading the brakes on my CR. While I was researching I looked at a few hand brake caliper options for the rear.
I bought calipers from Hi-Spec in the UK and went with 6 piston fronts and 4 piston rears. In the end I stuck with the stock E-brake setup on the rear as I found a larger ventilated rear disk that still had the hand brake drum inside it.
I was planning on using Hi-Spec's integrated handbrake caliper. They make a really nice 4 piston caliper with an extra mechanical caliper in the end of it for the hand brake.
Hi-Spec Hand Brake calipers
Just another option for you.
Cheers