There might be some demand, considering the increasing popularity of these trucks and of pro touring type machines.
They are definitely getting hard to find, but they are still out there for those willing to call around. After about 25 or so calls all over the country, I found a set in Washington at a salvage yard called Torgerson Wrecking. I had it shipped to my door for $105. I was very pleased. If I hadn't found that set, I think I would have fabbed something up myself. But there are those who won't want to or can't.
For anyone looking, don't forget to check all available applications:
85-87 1/2 tons
85-91 Blazers, Jimmys, and Suburbans
85-91 3/4 and 1 tons