Cover screw holes in pvc
As BrownRedHawk suggested white silicone will keep water out (paint silicone won't accept paint). White latex caulking is similar to silicone, but it does cover easily with paint. You could also try 2 part white epoxy. This will set to a solid patch that can be sanded smooth and remain rigid and weatherproof. I'd favor the epoxy and once dry paint it with an appliance spray paint to blend it in.