Saw a neat one in Memphis, TN at the Graceland Campground. Unfortunately did not get a picture. It was made from PVC pipe, was tall enough to hang the sign and their dog's names below. It looked like it was made from 1 1/2" PVC pipe.
Here is a picture of a similar project, you could modify the height and leg dimensions to suit your sign.
This came from another camper solving a problem they had, pretty neat. Check out the Instructable the guy wrote up here:
PVC iPad holder and mount for tent camping
Here is another possibility, closer to what I'm thinking of. Extend the height, extend the leg length, couple of "S" and eye hooks and away you go. The top (Photo A) photo is what I'm trying to get across.
I've been thinking of making something similar for our sign.
Hope this helps some.
Chris in Virginia