Rear camera cleaning

Has anyone found a method of keeping the rear cameras lens clean during this wet weather? 
Popping in and out of the cab to clean it has become a bit of a bind

I doubt if it's possible. The slab rear end of the van creates all kinds of vortices which inevitably deposit muck over the whole area. The little roof fitted to some cameras doesn't help much either.

The best solution I've found is a small bit of sponge on a stick. I can then quite easily give the lenses a quick wipe. If the conditions continue to be wet I don't usually bother. Quite often the lenses partially clean themselves in the spray, but if they don't I rely on the door mirrors - as I would have to without a rear view camera.