http://www.grandprixforums.net/water...-fix-6961.html or oyu could do what i did.
i took a thick plastic bag cut it and tucked it under the lip where the original flap is tucked in, folded it to the other side and caulked both sides at the top with a thin bead of caulk just to hold it in place, mines been like this for a year now and still dont leak.
ideally some kind of peel and stick rubber would work too, or some old rubber tube and rubber cement would work as well, just gluing a patch on the old flap, if you know what i mean.
