Back when I worked for Toyota (in the late 80's) we had a key punch tool that could make keys for any Toyota by only knowing the VIN. Understandably the VIN to key code info and those punch tools were guarded. That was also a long time ago and not sure that info and or knowledge to punch out new keys that way still exists. If it does, and you find somebody able to do it, that would be the easiest. Otherwise, the next easiest method would be to remove a lock cylinder from one of the van doors and take it to a locksmith. They can open it up and fabricate a key to match. If one key worked on every lock before, the new key they make will do the same. Not sure what locksmiths charge anymore, but a competent one can do that job in about 15 - 20 minutes. Tim
PS: If you're replacing the ignition tumbler, take the new one in with the door lock and have the new tumbler keyed to match at the same time.