The gze's came with aircon, might have been an option though. I'm sure someone has one lying around, just put a wanted ad for the compressor here and at twincam.org. To fit it you'll need the condensor as well. You'd then need custom pipes to run from the compressor to the condensor and then to the interior, as the standard ones for the gze will probably be different.
I've probably missed some parts here but I think those are the major ones.