Help/Info on part
 

My 420 SEL (1989) has been cutting out lately - just stopping while driving. Sometimes I can restart it right away, or if I'm on a hiway going 70+ it will restart itself. I had the fuel filter changed and the mech said that should do it. But the other day it stopped again and another mech who owns a MB told me it was definitly a "Hydro Pneumatic Activator". he showed it to me and said to hit it with a screwdriver if the car dies. He even carries an extra one with him for his car. Where can I get one of these? Are they expensive? (No bigger than a box of matches). Will a used one from a salvaged MB be alright?
Thanks, John