What year is your car, sounds like youve got an early base model there, 1.1L maybe??

Do you have many drilled holes on the passenger side where the servo mounting brackets would be? Maybe you could pull the linkage and servo out of a mk4 RST/XR3i and fit the whole lot, you'll probrably have to get new brake pipes made up to reach it.

On the other hand if you could get hold of a servo and linkage from a LHD escort you could possibly be able to adapt that, but there could be clearance issues