I was experiencing the same problem/creaking on my 06. After many failed attempts I think I finally fixed it! The noise was coming from the top corner of the rear window, and was worse on hot days on rough roads. (Pleanty of both in Wisconsin)
Peel back the head liner by removing the two corner plastic fastners.
In the top corner of the rear window there will be a metal tab under a plastic piece that is attached to the window.
SLIGHTLY pry the metal tab downward with a screw driver away from the rear window and plastic peice.
This should provide just enough space between the metal tab and plastic piece which I found was where the noise was coming from.
I also sprayed a little WD-40 in between the tab and plastic just to be sure.
I drove the car before the fix and the noise was horrible. After the same test drive following the fix the noise was gone. finally! I was hesitant to start prying on things by the window but after looking, you are not affecting the seal. I have read that the tabs are just for alignment when installing the rear window. The noise was VERY ANNOYING and I read this is a common problem in the 9th gen.
I will post following a long term test of the fix.
Hope this helps others.