Silicone Caulk. Comes in tubes, the type for sealing aquariums or glass in the bathroom and so on (same area as glues and fillers) . The right type is clear and you will find "100% silicone" printed on the label. BTW, slow to cure in hot weather , cures very fast in high humidity.
As I pointed out before, thinn it because the thicker it is the easier it is to peel off.