Do a search for "Storm Jacket Camera Cover" I ordered mine directly from the company. I no longer have a link for them.
I have a 26 ft. boat and also have used zip locks on the Chesapeak Bay. But purchased a Storm Jacket Camera Cover a couple of years ago with a clear filter. It keeps things dry and the can be washed when needed.
1 if it was cropped try adding a little area past the tail end.