I prefer the one from Apple. Cheap is where you find them. Did you try amazon?
Can anyone recommend a good keyboard case? I just bought a new iPad 3, and am looking to use it for note taking at school. I would prefer something that has the most quality for dollar, since I am a poor student. I have looked at the Zaggfolio, and am surprised that most of the "name" brand cases are $100+. Is there anything cheaper?