I have the exact same issue as you right now on my 96 GTS. I've been calling every vendor I could find and even talked directly to GMB. They stopped making them last year due to low volume and any online vendor who says they have a GMB for sale doesn't, as they will treat it like a special order and try to get GMB to make and send one but they don't anymore. Same with Bosch. Steve was right on with viperpartsusa.com, very knowledable about the Gen2 pumps and only have 5 (4 now as I just ordered one) in stock. They are the "new" mopar 2001+ design based water pumps. Not remanufactured, but actual new pumps. Once they are gone, don't know what options we will have. Limited remanufactured I suppose, but trust me, you don't want to go that route. I did in 2013 and it broke again this past month.
I've got fingers crossed the new one I get from viperpartsusa.com has the better design like what GMB was making. I'll post pics when it gets in and we put her on to let y'all know.