Help need Idler arm and air conditioning parts

Hi, I'm new to the forum, my wife and I just bought a 1979 Airstream Excella 28ft. Everything checked out great when we had it inspected except for two things. We need to buy an idler arm for the bell crank and we need to buy an air conditioning air compressor and dryer so we can have the a/c redone and retrofitted for the newer ac freon. Our mechanic found the idler arm but the cost is $250-300. The mechanic is pretty sure there are cheaper idler arms. He has not been successful in locating it. Does anyone know of any companies that have these parts and are reasonably priced? Any help would be appreciated.

Thanks