I know it's been a while since you posted, but I have firsthand experience with BestBattery.com. I ordered the LP-E4 battery and charger combo through eBay. I think it was about $56, which seemed like a great deal. It wasn't. The battery did not fit the camera very well at all. I had to force the weather seal tight to get it to latch. And then, it still didn't fit right. Also, the camera indicated it could not communicate with the battery, so no level information could be shown. I also got problems with high-speed drive and some other issues. The charger had something loose inside rattling around. It doesn't seem to charge the battery.
I know the OEM stuff is super-pricey, but I'm thinking it's well worth it.