One thing you might try is to keep a skunk in your van and poke it with a stick every day or two to keep the smell fresh. That way, when the officer pulls you over, not only will he NOT want to search your van, you will have an excuse for the red eyes. If by chance he does want to press the issue, ask him if, while he's searching, if he finds that skunk that keeps hiding under the pile of tools just out of reach you'd appreciate it if he'd remove it for you.
(This post does not mean the Pastor endorses such activity. The most prudent thing to do would be to not have illegal substances in your car and not break the traffic laws)