Default Looking for new replacement EB20 battery.

I recently received my mother's well conditioned, but long used Atrix HD. I have already unlocked boot loader and rooted, butthe battery is about had it. In 30 min of general use, I drain 20-30% battery, or more. I even lose charge while charging. I know how to replace the battery, but the batteries that I see on Amazon vary in brand and amperage. Is there any specific EB20 battery that I should go with, or is the amperage the only thing to look for?