When I picked up my VX it had only one intact plastic screw holding the spare tire cover (and one in pieces), and while looking for a DIY alternative, I decided to try and repair the broken one I had. After several failed attempts to repair the break with various epoxies, adhesives, and contact cement, I tried filling the hollow shaft of the screw with a compound called Plumber's Goop. This proved to be a little soft, so I put in a carriage bolt to use as a spine and it seems to have worked just jim dandy. It takes a couple of weeks to completely dry but it's extremely solid now.
As a preventative measure to forestall the eventual break of the remaining screw I gave it the same treatment, and it seems a LOT sturdier than it was originally.
Maybe this can save someone else a little money, it's fairly cheap preventative maintenance, and it's completely unnoticeable when the screws are in place.