Lots of places sell replacement glass rubber intended for this purpose. Where you get it may be determined by what car or truck you have. Most chopped cars can use the original type rubber cut and super glued back together.

www.softseal.com is one option, www.robertsmotorparts.com is another, there are probably 10 resources to obtain automotive window weatherstripping. If you want to tell us what car/truck your looking for the weatherstripping for, we can probably better direct you. Gene