It took me awhile but I finally ordered the 105Ah battery online. There were multiple people selling them online but they wouldn't ship batteries.
I finally found BMW of Chapel Hill and bought it from their eBay page. They will ship it to me.
There's a SIB that came out early this year that affected my car and BMW recommended upgrading to the 105Ah battery.
http://www.bimmerfest.com/forums/sho...5&postcount=12
They called out a battery part number from the OEM catalog which was cheaper than the collision catalog that was provided in this thread.
61-21-2-353-814 is the same OEM East Penn 105Ah AGM battery.
Here's the eBay link where I bought it from, I just bought it today so I will keep you guys updated after it comes in. I also purchased the additional clamp that the SIB calls out needing if I upgrade to 105Ah from 90Ah.
http://www.ebay.com/itm/281437759832