Welcome to the Bunnings Workshop community @Errol. It's fantastic to have you join us and many thanks for your question.
I would hazard a guess that our helpful members might need a few extra details and potentially an image to assist you with your question. I am not aware of an aerosol spray that is specifically marketed for sealing leaky windows. The closest product would be Rust-Oleum 312g Clear LeakSeal Flexible Rubber Coating Spray. This is an extremely versatile product for sealing a range of leaks and gaps around the exterior of your home. The effectiveness of this product will depend on the style of the window and how the water is penetrating through it.
Please let me know if you need further information or had any questions.
Mitchell
