Years ago they made an item that was called a camera-blimp I believe. It was a loose fitting cover made of a thin layer of foam that the camera fit into, yet had the appropriate openings for your hand and of course the lens to stick out of. I don't know if they still make them, I would suggest contacting B&H Photo, if anyone has it, they would.
Option "B"---a small camera like the Panasonic FZ35 that has an electronic viewfinder(no mirror) that is virtually silent if you want it to be.