I've never seen a Chrysler that you can program a new remote to without at least one other working FOB. The dealership service department can do it though....at a price.
Did you buy from a private party? Any reason why they don't have the FOB? I would be concerned that the seller is keeping the FOB to easily steal stuff from you later. It might behoove you to disable the alarm system completely if that's possible. I know in my Neon I can just pull a 10A fuse, I would imagine it's the same for that van (although you should really double check so you don't accidentally set off the alarm and have no way to disable it).