You mean the rubbery seals / trim around the windows? From what I know you cant get it. Its part of the quarter windows and they are not available anywhere. Thats why I have stocked up on 2 sets of used quarter windows and got lucky enough to get one NOS quarter window. Hopefully somebody someday will reproduce these.
The only thing I can think of is to put up a WTB add for good 1/4 windows. I wish I could help but I have my dads car that needs the 1/4 windows for his and I want to keep a set for mine since they are difficult to come by. Im sure somebody somewhere has a set they will sell you. Unfortunately these windows are not the same as Montes, cutlass, etc.
How bad are yours? Are they just shrunk? Can you re-use them?