Covering cal vent holes

[forestb]

I have speakers installed in my kick panel vent holes and I want to figure out a way to block off my cal vent holes in order to keep rain from getting in. Originally I built cups for the speakers to sit in but they are restricting air flow behind the speakers which is making them not function properly so I am going to have to cut a hole in the cups. I need to block the cal vent in such a way that it can be removed to access the windshield wiper mechanism and I don't want to cut or weld anything. I know that they sell panels that don't have the slots in in them but that will not keep the rain that runs down the window out of the holes. Any ideas.