Well, mine came out and I just stuffed it back in. Seems to work; doesn't leak or whistle. I figured I could put some adhesive on it if it came off again, but it has not. I agree that it looks to be difficult to get and keep the glue in the right place, but you wouldn't need much, particularly if you could also apply a little silicone on the lip to keep it from sticking to the glass.

No way I'd pay to replace the whole glass.