verizon wireless website has it, but its out of stock. best bet would be to go to your closest store and see if they have any on hand. hope this helps!
Seidio makes extended batteries and cases to cover the extended batteries. I have one on my Droid Incredible, and one not currently installed on my Droid 1. Good quality batteries, they come with a free extended battery cover BTW, and good quality cases.
Check Amazon.com first - they're usually cheaper - or seidioonline.com