Those are interesting Brent but what I'm thinking of is not something to fill the drain hole so much as something square to fill the entire recess and make it flush with the surrounding deck. A wood or plastic grate with screening on the bottom or with something like you linked to filling the hole.
I can easily make something but , as a new owner , I was curious to know if factory issue was with a finished grate or just the wide open hole that I have.