Eric, GM doesn't carry them any longer. I see them on eBay (NOS) quite a bit, but they have been going for $100-150 each!!
On your door panels, do you need them with power options (windows/locks), map pockets, or manual windows? I ask because 77-87 are all the same, but they come in all sorts of different configs based on the options of the truck. I have a couple sets of panels off 80's trucks, but they have all the holes for pockets, carpeting, PW/PL, etc..