Fred's comments are a good model but still leave you presenting something they have already told you they are not interested in hearing or acting on.

I think the construction helmet worn at the field might do what you want. Think about it, when seen folks wonder why. Sooner or later they will come to the correct conclusion and you will have lead them to a safer method of doing business with no grief. If they are too stupid to figure it out, they are too stupid but you will have some protection.