I was searching online looking at rebuilt ones for ya, now I see why you want to buy some used ones. Holy shit rebuilt one's are expensive. If all you can find are leaky one's, rebuild kits are less than $10, pretty easy to do too.

If you live in Seminole, there's a salvage yard off of 118th ave called Magic Auto Parts (or something like that) and they have a red s13 hatch all the way against the fence on the east side of the property. The car is on top of two others, but two weeks ago it still had all the brakes on it.