Question on Bumper Stickers

[Richard Stouffer]

I want to have a sign on the back of my fiberglass motorhome that shows I'm monitoring 146.52. I only want it there when I'm actually monitoring the frequency.

Is there any type of material that will stay in place on fiberglass yet be removable like a magnetic sign. Of course I want to be able to put it on and take it off an infinite number of times.

Thanks