I tried the cup holder from my Trooper in the VX, and it fits just fine. The color is almost exactly the same as the carpet, despite what the photo looks like. Isuzu may even offer one in black, but since I never have anyone in the back seat, and it can't be seen from the front seat, this one will suit me just fine.
To install it, you just remove the ashtray, and screw this cup holder on in its place.
Closed:
http://tad.grosvenor.org/gallery/VXMods/CIMG1020
Open:
http://tad.grosvenor.org/gallery/VXMods/CIMG1021
If you are eating fast food, it isn't the most conveinent spot for a cup holder, but I more just want a place to put a bottle of water so that it won't roll around on the floor. It is easily reachable however.
-Tad