Assuming you don't find one at the airport when you arrive, you could get one like this:

http://www.amazon.com/T-Mobile-Tmobi..._bxgy_e_text_b


Then follow this procedure:

http://www.t-mobile.com/shop/plans/activatecodes.aspx


T-mobile is much more helpful for prepaid and SIM only services compared to AT&T.

Not to mention that the T-Mobile 3G spectrum is compatible with the N9 (pentaband, so no great achievement) as well as the much harder to please N900.