Don't limit your search to a VX with a roof rack - the VX roof rack (towers & crossbars) is readily available from any Isuzu dealer. They're pricey (I paid $355 for mine in January) but not hard to find at all. A couple of used ones have come up on eBay in the last couple of months, as well. Note that Yakima made the rack for Isuzu, but they won't sell you one directly - you have to pay Isuzu's premium price for it. Isuzu will also sell you some of the attachments for it (such as a ski/board rack), but I don't know if these can be purchased through Yakima directly. I think the VX's crossbars are exceptionally wide, which means they may require special attachments.

Good luck in your search!

The caps for the roof rail mounting points might be more expensive than they're worth if you go through the dealer, but they pop up for sale here every 2-3 months as well.