The Deka East Penn battery in the link below fits and works perfectly. Deka East Penn was an OEM supplier for BMW. Go to a dealer or independent shop for the battery registration.
Sign up for their newsletter and get 10% off your first order. Comes to $188.95. No tax and free shipping.
http://www.autobarn.net/eas9agm49.html
Deka EAS9AGM49 is the same as the East Penn 61217594976
http://www.realoem.com/bmw/showparts...99&hg=61&fg=30