Why not just fabricate one? Lexan is very workable, particularly if you're looking for a single piece cover.
St. Tammany Glass carries lexan. I'm going to go there this week to pick up some material for new portlights for my boat and for Hot Chocolate. Let me know if you want me to get a price for you.
I have a plywood companionway cover that I can bring to the club tomorrow night, if you would like. If it fits your boat, we can use it as a template.
Of course, you can try to find an existing cover, but where's the fun in that?
