My favorite, and by far the most effective I've found is pretty basic. Ziploc bags. The gallon size is plenty big for a body with shorter lenses attached, and the 2-gallon size will seal over a body with lenses up through 300 f/4 attached. Put the bagged camera and lens in whichever carry bag suits your needs, and always carry spare ziplocs in your kit.
For waterproof shooting even on a tripod, add a lens hood, pull the bag over the lens and body, then cut off the lower corner of the bag just large enough to allow the lens hood to fit through. Snap a rubber band around hole in the bag to attach it to the hood, and fire away. The 2-gallon size is large enough for your hands to reach in and manipulate the camera, meanwhile the back of the bag is tall enough to serve as a hood over the rear body face. Between shooting sessions, zip the seal and snap on a lens.
Nice to find something so very cheap, compact and effective. May look like hell, but not as bad as a wet camera in a shipping box headed for repairs.