Are you sure you need the receiver? Which unit are you installing the card? If it is the one in the PC/XT, what you really need is the extender, however, if you're talking about the card located in the expansion unit, what you want then, is the receiver. They are not interchangeable.
Extender cards are not that easy to come by. I have a spare extender and receiver, but I am keeping them for an upcoming project. Extender cards do occasionally pop up on E-Bay, and there is one member here I know of who might be interested in selling a spare he purchased not too long ago. Once we know for sure which card you need, I will forward your contact info to him via PM. If he is willing to sell, either he, or I will then notify you.