Better battery for HTC G2?

-This is reasked question because all I got b4 was "just get a new phone" and spam. I want a SERIOUS ANSWER! This phone is brand new and there's no way I'm getting a new one. Anyway, is there anyway way I can get a better battery for my HTC G2 by T-Mobile? It dies way too qucikly and drives me crazy that I have to constantly charge it. Right now it still has the Li-on battery that came with the phone. And does charging the phone while its on gradually reduce battery life? Because the charge seems to be lasting less and less longer.