Pretty much everything you see on ebay that is new is aftermarket, but if it were me I would contact several of those sellers and ask if they would either source, paint, and ship OEM parts, or allow you to ship them OEM parts to paint. There are several challenges to this issue. Color match can be a challenge despite painting with the factory formula because your van has been exposed to the elements and experienced subtle changes to the original color, and shipping painted parts without scratching or scuffing them can be difficult.
Another route I would explore is supplying the OEM parts to a local Maaco shop for a cost effective finish. Make sure you choose at least their mid level paint as the cheapest paint is just that, cheap. I have a buddy who owns a Maaco franchise and he hates the cheap paint so much he refuses to use it and just substitutes the better material when the customer insists on the cheap paint, but you can't bet on that always happening.