I'd use an ordinary silicone clear sealant, but it is not 100%. You could finish off with..........wait for it.........."Capt Tolley's Creeping Crack Cure"! It does seem to work for sealing small leaks; esp. in the bottom quarters of the screen. Available from 'Frost' if you're not too embarrassed to ask for it
I need to reseal the exterior window/door rubbers. The workshop manual says to use Bostik 1261 unfortunately it is no longer available. Can any member recommend an alternative please