I'm sure you are gona think this comment is rude but since you are leasing this Blazer why is your underwear in wad? You haven't spent 30 to 60K to outright purchase your Blazer like me and others have. Of course with a lease you will return yours as to where the rest of us can't just return ours.
After a bit of research on the net and a few phone calls, the window can be replaced for around $300 or so. (I'm sure it'll cost more pending where you live like CA or NY. I'm in TN) That's less than some are making on monthly payments on their Blazers. If you can afford to lease, and it bothers you that much, replace it yourself.