u/Federal-Landmine

Hey everyone! Recently bought my friends father in laws park avenue. Its a 1999 ultra model and Im having a blast fixing it up. Just replaced and painted the right side mirror, new alternator, new tires...

Only problem is I cannot identify this part. It may be super simple but I cannot find a replacement anywhere. If anyone can help identify the name or where I can get one ill be very grateful. Some pictures attached. Its a black rubber but putting in weather strips isn't yielding good results. Thanks all.

Edit: ive identified the part as Driver Side Front Door Lower Weatherstrip - GM (25634571) but cannot find one anywhere. Anyone have any suggestions or know where i can grab one? Thanks alot.