Where are you from? The best places for that sort of thing are the rv surplus outlets in Elkhart, IN and White Pigeon, MI just across the line. There are about 5 places up there and I've been to 3 of them. There are great deals to be had, but you have to watch, not everything is necessarily cheap, you gotta know what you are buying.
Bontagers usually has a supply of dinettes/cuishons in stock:
Bontragers Surplus Inc.
Here is a list of RV surplus / salvage dealers nationwide:
RV Salvage
Great looking truck, I particularly like the way it kicks up in the back to match a full height trailer.