Where to buy dash A/C parts-1994 georgie boy P30

I have a 1994 georgie boy pursuit 28' that I would like to get the dash a/c working on. I took it to my local repair shop and they did get it blowing cool, but not cold. The expansion valve needs to be replaced, along with the high pressure switch and receiver/dryer. It is on a P30 chassis that originally came with R12 refrigerant. It has been converted at some point to R134a. So, I took a trip to o'reilly auto parts which has always had what I needed. Not on this trip...The expansion valve and receiver/dryer both look nothing like what I pulled off of the coach. I have been looking on ebay/google and have located the reciever/dryer and I think I found the high pressure switch. But, the expansion valve is what is throwing me for a loop. There is no part number anywhere on it, and without that part the a/c won't be working. Anyone have any idea of where to buy this expansion valve? It is an aluminum block with 4 lines running to it, two on each side. Any help is greatly appreciated.