Is this same stuff used on vans and trucks? That stuff would seem to durable the surface of a vehicle gets pretty hot in the sun.
I have seen it on ice cream carts but not steam carts. How about just doing the side facing customers? You can make a nice colorful sign to cover any area you want. Go to a sign place they can answer your questions.
Now the plumbing issue. I don’t understand what they are talking about. Do you have exterior sinks with exposed pipes?