1992 Mazda B2200 SE-5 servo diaphragm bad

Whenever my 92 B2200 truck is running at idle and I put my air condition on, the engines RPM fluctuates constantly (800-1200 RPM). I checked the engine and its the servo diaphragm in the back of the engine just below the carburetor not holding. Does anyone know where I can get a replacement? I've checked several junkyards and even google to see if I can purchase a replacement but have'nt had any luck. Any help I can get is greatly appreciated.

I already sold the one from my stock carb, then later sold that carb too.

I'm in Arizona where most of the B-trucks had AC, so post a good photo that shows where that part is located on the carb (I can't remember), and I can try to look when I visit the yard about Dec. 28th.

So you're sure it's not the actuator for this on the passenger side of the engine compartment?

This is what is bad whenever I turn on my AC.