If the passenger side is still attached, I'd suggest taking it off and reattaching it with fresh adhesive. The original was attached via foam (glued on both sides) and it deteriorates over time, so you days are numbered on the other side.... Windshield adhesive seems to be the popular choice.
If Fred doesn't have one, I can look around my garage, but pretty sure I sold all the ones I had hoarded as I don't have a Buick anymore. Now if you want tan interior parts, come talk to me as I'm trying to re-home a bunch of stuff! (had a tan interior and car got totaled)