Whether they buy them or make them, the seal material is going to be some satndard type available from a seal/rubber supplier. Neither the coach builder nor a window/door supplier makes their own rubber seals. Identifying the right type might be a challenge, but they are available.
Yes, there are usually adjustments. However, back in that timeframe there were numerous door noise complaints and the basic issue was simply inadequate structural rigidity in the door area. The frame shifts with movement and the door moves in the frame, so some leakage is common. Eventually most of the manufacturers improved their designs to reduce or eliminate the problem, but many lower or mid range coaches in the 90's and early 2000's have the wind noise problem and a fix rarely lasts long.
You will have better luck with a high end model (and they don't cost much more at that age), but some of them weren't perfect either.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL