Trying to figure out a good way to keep the sun & weather off the cab, especially the rubber window gaskets & such... For now, I'll use a tarp and see how it goes.
one cool trick i saw....not for covering the cab but for providing shade while at anchor....was to take a really light material (parachute fabric in this case) and make a rectangular sheet that can slide over your antennas when they're in the same position as in your pic. packs nice and tight too because of the material it's made of.
doesn't help with your question...but might help if you need shade on the deck while at anchor.
other than a tarp, i'd say a custom cover (which is what i got after re-gelcoating my Radon) or a carport style setup.