Although some may beg to differ, I say that you do get what you pay for, and 3rd party batteries can never be as good as the originals. Be warned that you may be setting yourself up for a very frustrating experience.
But yeah, for what it's worth, Eastgear seems to be the popular choice. I got 3 batts from them, and they weren't even half as good as the originals.
I find it a bit risky to follow a recommendation that the recommenders themselves haven't tried before.
Cheap is not good. Good is not cheap. (Generally, lah). Just like many, I have gone the "cheaper alternative" route before, and end up spending more on buying more 3rd party batts, and then eventually settling for the originals anyway.
However, if TS insists on getting 3rd party, I suggest he/she sticks with EastGear. At least they have a returns policy, which DOES come in handy when you receive a dead batt.