Not much in the way of aftermarket plastic body parts for 2-year-old minivans.  Find a junk yard that specializes in your brand, and try to get one from there.  Be aware that it may need to be repainted to match (as would an aftermarket part), so that may eat up any savings vs the dealer.  At least find out exactly what the dealer will charge, so you have a baseline price.  Check several dealers in your area, too, because each dealer is free to set their own price, and there can be considerable variation.

-Troy