for example brake boosters etc. I just selected as a sample an 535
http://www.rockauto.com/catalog/racatalog.php

-1 CARDONE Part # 532603 {[Power Brake Booster] w/o Master Cylinder; Reman.}
w/ATE Brake Booster

Price Core Total
$191.79 $20.00 $211.79

Seems to be an alternative.