I bought my Blazer rear hatch from Brothers' Truck Parts, of Corona, CA for about that much. It came bare and I had to get the extra latches and relay rods from a junker in SF -- since much of the OEM stuff was damaged when I thrashed my original hatch. I reused the back window, mounting it in new hatch glass rubber and hatch-to-body rubber gaskets, either from Brothers' or LMC. Also you might try a parts wanted request @:
http://www.ColoradoK5.Com that's a board that's dedicated to Blazers and they have a '69-'72 First Gneration forum. Friendly and knowledgable folks. If you get lucky, a used whole top can be had for the price of the re-pop.