Stop in for a cup of coffee

Good morning, retirees and the rest of us wanna-be-retirees...I was thinking just now. I used to have some Por-15 which I used in this way, is there anything else I can use (cheaper and I don't need much) to let flow into the space behind the trim of the back window of my Fury? Water collects there as we know and I would like to avoid rust.