Rear window seal ? where to buy and how to fit ?

[Mito-Maniac]

Hi, just got my hands on a P reg GTI and the rear window on the drivers side leaks in as its not fitted properly and the rubber seal is not in place, its just help in with putty as far as i can tell, just wondering if anyone would know where to get one of these seals from and how to fit them ?

Thanks in advance
Dave