I looked around on ebay at various center cap covers and found some that were close to the right diameter and looked like they might wind up the right height if the clips were removed and installed with adhesive. Nice chrome and slightly domed plastic and under $20 for a set of 4. The "bonus" was that they had GMC logo in raised perimeter, all chrome, no paint, decal, reflector, so why not.
Here is a cap as received.
I removed the spring clip and cut off latches, which was very easy to do, and then gave them a quick sanding on a flat sheet of sandpaper to even it all out for better location.
It was raining nothing else going on, and I thought they looked a bit plain, so decided to try to duplicate the "reflector" type thing GMC does. After a bunch of messing around settled on using glitter paint with clear enamel over it, brushed on with an art brush.
I then just stuck them in place with silicone and used black silicone to fill the small gap to the Wheelskins. They turned out nearly flush with Wheelskin and the dome certainly makes them look better.
Done and on the bench.
Done and on the van, please ignore the filthy tire that has not been cleaned up after the last two trips
All and all not a bad way to spend rainy time, as it does look nicer, but the modification to make it all one piece will certainly be more useful. Now the whole thing can go in the laundry tub to soak clean instead of squatting, cleaning, and polishing wheels.
Doing the Wheelskin modification should work on all the Chevies that have them installed on the factory wheels and centers, including the ones from the factory like Roadtreks. You could probably even find a Mercedes or Porsche center cover to put in them if you should so chose....
I would say that now that all is set how to do the changes, I could do a full set in about 4 hours of labor, but would have two periods of adhesive setting in between.