1983 500SL idle control module

I need to replace my idle control module. My mechanic couldn't locate a new one for me. He thinks if I get one I can easily install it myself in about 1/2 hour. Right now the car idles too high.

Can anyone tell me where I can buy one of these idle control units?

Thanks in advance, Mark

P.S. It is not the idle control valve... checked that already!