Ah OK, so it's not rear door rubber you are after, but the rear quarter panel seal. 406, so what year is the car, and what is the chassis number (via PM if necessary), and why is the seal required?
After 1990 very likely to be bonded.
Why has the dealer refused to supply the information to you? What reason did they give? Have you tried ringing a company such as Autoglass that the dealers contract out glass replacement, or looked at the windows for the manufacturer, and tried to call them? Have you tried to contact the Pugeot owners club?
My dealer is very accomodating, and gives discount, or throws in freebies, I took in my ancient '87 Celica, with all the new Lexus about, and said, bet you don't support these? They said No problem, see them daily. When I had an Avensis, they fixed stuff I didn't even know was broke! for free. Don't understand when manufacturers/dealers refuse to help? They go through the blueprint design on the computer with me to highlight the correct part. It's hardly like they are telling you how the security system works!