Reminds me of the one about the guy who goes into the mens room at a country/western bar and comes out with one of those paper toilet seat covers over his head and proclaims loudly "look everyone, free cowboy hats!"Trucker jokes work too.
One time on a trip I stopped for gas and food and a rest break. In the men's bathroom there was a coin op condom dispenser. Some one had written on it in bold letters, "Swift driver's shower caps."