PVC Lamp/Name Board Post

Go to the Handy Hints, Gadgets, Projects and Gizmos thread and there are examples in it. They are not for a solar light but could be easily adapted. Basically they use a 3" Toilet Flange and then an adapter to go to 2" PVC pipe. At the level where you want the wood sign you put in a 2" Tee and reducer to 1" for the sign holder and add a 1" cap on the end. You would need to adapt to whatever fitting you have on the solar light on the top of the 2" PVC. Paint it to suit yourself. If you end up making one, please post what light you end up using. I have been thinking about making one but was planning to use a 12 volt bulb in a regular outdoor fixture mounted on a PVC pole as described above.

Not sure how detailed, expensive, or DIY you want it to be.
You can make one with one of those small solar (sidewalk) lights that they sell at Walmart, and just stick it into a 3/4" piece of PVC pipe that has been put into the ground.
A "Tee" in the upper section would allow you to put a horizontal pipe, with a sign hanging from it.

All told, you could probably make it for about $20-25. Of course, you can also get more elaborate, and "supersize" it, but that is up to you.

The nice thing with the PVC, you don't have to glue it together, so you can pull it apart to store it in the RV

You can also get a piece of 1/2" rebar rod, to drive into the ground with a hammer, and then place the 3/4" PVC over it.

Happy Camping:)