I used stock front backing plates. They were like $10 for the pair from a junkyard. Then I had a machine shop expand the center hole and drill the 4-bolt pattern for about $20. Naturally, they hold stock front rotors.
I did this for a 14B S/F, so the machining would be a little different for a 10B since the axletube is smaller.
My whole rear setup was about $120 for calipers, backing plates, pins, flex hoses, pads and rotors, hardware, etc. and all of the parts are available at any parts store except for the backing plates and little brackets that hold the connection between the hard lines and the flex hoses. Everything was brand new except for the backing plates, but with some cleanup and paint they were as good as new, anyway. If I had more tools, it would have been even cheaper.