Master cylinder for 1974 Dodge Chasis class A

Sound Choice wrote:
HELP...HELP...HELP!!! I have a 1974 Cobra Class A MH on a Dodge R-50 Chassis. It has what appears to be a cast-iron?? master cylinder with "air/vacuum"?? assist, that is leaking. All the parts people say the part is obsolete and no longer available...the Salvage yards look at me like I'm NUTS...and the local one of the local RV service dealers told me if I had it towed in they would probably tell me to tow it back out! Anybody got any help for an old guy with an old RV in the Kansas City Mo. area? TNX Kc