Possibly same shop that sells hen's teeth.
Seems everyone wants them now!
Try CaliCampers, they may have some around....BUT....you'll need new tyres if from an old van.....tyres should be replaced after 7years.....5mm tread or not...the rubber will be perished!
GOOD for you to want rid of the 18" Audi stuff though.....VERY few are van rated, and 18's on a T4 just don't work.
Also, search for Collese (think I spelled that correct, forum member), he "collects" various rims to band.....maybe he has some original T4 ones?!?!?