Try Phoenix Trim. They have a vast selection. Scroll down and look at sponge rubber seals. These are skinned rubber so will not absorb water. I used one on my old classic and it created a perfect seal, even with an irregular boot lid shape.
Their website has been improved recently and they also do downloadable sheets of cross sections which are to scale full size if printed on A4 paper which is really useful. Peter.
https://phoenixtrim.co.uk