Batteries from Amazon have been great for me
I bought two replacement batteries from Amazon (I paid close to $5 each, they're now closer to $4). They both work flawlessly, with one delivering way more hours than my original, which still works fine.
I also bought two external chargers on Amazon (a drop more than $10 each when I got them). Those work great too (slower to charge than plugging the phone into the wall).
My best experience is using the external charger through my laptop's USB port. It takes a full 4 hours to charge the battery, but man, the battery holds the charge longer than when it charges quickly through the wall.
Now, I rarely charge the phone itself. I just swap batteries, every day or two and carry a spare with me at all times.