Kind of redneck looking but versatile and highly functional:
We carry 2-gallon ziplocs (the jumbo size in some brands) along with rubber bands. Cut one corner from the bag, slip it over the camera with the lens out the hole and use a rubber band to secure the bag to the lens hood. The 2-gallon size is plenty big to allow your hands in for operation. I've used them on lenses out to 80-200 zooms. In between shots, zip the bag closed, even on a tripod. A box of 10 or so cost less than a premium coffee, and you can always have a few rolled up in a camera bag for emergencies. Even handy for full camera protection in heavy rain if you don't cut the hole in a corner. The bags come into their own too, for protecting cold cameras from condensation when you return from the cold to a warm house or car.