Rapid prototyping companies (I am good friends with the manager at a local one) can do basically what you're doing without annoying your wife
They can take a 3D design, create the part with stereolithography and other methods, then make RTV molds for short-run production (i.e. VX owner quantities).
I have Solidworks 3D software, and the rail covers, compared to tiny medical devices I have designed, are like tanks. The rapid prototype shops have so many cool materials now that there is bound to be one that will remain strong in thin cross section, won't fade in UV, plus the rail caps aren't load bearing since they have to be removed to put the roof rack on. There would be no need for injection molding, which is good since I doubt anyone here would be in to paying some of the $10-15k for the tool to be made.
Total cost for a part like the rail cap and then runs of 100 or so might be <$2000 with a per part casting cost of $10-20 off the top of my head. Really the only trick is to get the design in to Solidworks or some other CAD program accurately.