I think there are three different styles of glass.
First is the one-piece glass, which uses a single gasket that goes all the way around, just as you's expect.
Second is a two-piece glass and vent window, mounted separately with individual gaskets, in the same opening. There is a chrome strip that goes around both pieces, making it look like one piece. This is the style I have, and new gaskets are impossible to find. Fortunately, my original gaskets were pliable enough to re-use. I'd like to replace the chrome strip, though.
Third is a window and vent mounted in a one-piece aluminum frame, which gets installed as a single unit, with a single gasket, like most windows. I suspect this gasket is very similar to the first style, but I don't know if they are interchangeable.
I heard BJs was working on a source for the gasket for the one-piece glass, but I don't know where they are with that.
Good luck!
Now I must hurry on... for there they go, and I am their leader!
'78 Cherokee Chief
'82 Scrambler