I've had very good luck with my Tuff-Luv leather case. Amazon has several versions and colors now. I ordered before Amazon said they had them in stock, but Tuff-Luv shipped it about 2 weeks early. No problem in security making me take it out (about 10 airports).

Note: the link is for the faux leather, I bought the more expensive "real" leather and have had great results. I really like that the case allows you multiple angles when viewing in landscape mode, makes for better viewing on when using different tables, seat backs, etc. I originally heard about the Tuff-Luv in another FT thread, but don't remember which one.