Is it possible that the moisture is on the external portion of the lens? Air turbulence may be getting moisture on the lens even though it it is facing rearward.
Here is a suggestion: I spoke to my neighbor whom was polishing his truck and asked what he was using. "ReJex" was the reply. He went on to say that he uses this on his truck glass, boat windshield (plastic) and his fiberglass boat (used on salt water) as-well. I tried it and it does a phenomenal job of sheeting water off both glass and plastic windshields. A coating of this on the camera lenses may solve your problem. Besides sheeting off, it does not fog, does not leave a visible film, and does not damage the surface of the application. It is not cheap, but it may be worth a try.A little goes a long way.