I've had the calipers and rotors from a 2006 or 7 or something mazda6 for a while now, and i've also been without an eBrake. The cable's snapped somewhere, when i fix that i'll see if i can re-route the cable to work with the mazda6 rear calipers.
My whole set up was around $300 if i remember correctly, and i might not since my dad claims it was no where near that much. Parts came from a junkyard in florida (bought off ebay though- one of those listings with the same picture of a junked car for each listing, but a different part for sale... and for some reason a guy in a panda suit) off what appeared to be a freshly junked car. Came with Calipers/brakets, rotors, and for some reason 3 pads for the front with all the clips and shims. I don't know where the 3 came from, but they appeared to be brand new... but alas, just 3.
I'll spam it all over the internet if i can get the cable to work eh?