Good ideas from Tartan ...
I simply pin min to a piece of foam core and they lift out the pin to see the reverse.
As Tartan said, it could be different in your area .... you would be best to contact someone on the committee for that section at the Fair, and ask what are acceptable ways to meet their requirements. I am sure you will find they will be glad to help as most Fairs are thrilled to have new exhibitors and will do what they can to help encourage your participation.
Good Luck!