I was just researching rebuilt calipers a few weeks ago when I was getting ready to rebuild my ATE unit. I was able to order Bendix calipers locally through my O'Reilly (in stock in local warehouse) and available via Amazon.com (example here for C126 560SEC).. Amazon wants like $70 apiece for semi-loaded Bendix units. I don't know how that compares to other marques, but I would have no problem paying $70 for a qwality rebuilt caliper.

Cheers,
Gerry