Available from the Motorola Store for $49.95. Stick with OEM from Moto...
Let us know how it works out for you?
It works fine. Friend of mine has it. It's < 2800 mAh and it doesn't make the phone too much bigger.. The battery door is very secure, very. Recommended. It does make the phone quite a big heavier, though. Atrix 2 with that battery is easily 3x as heavy as my Skyrocket.
I never recommend anything but stock extended batteries, personally.