Re: Extended battery users
How is the stock battery holding up for you now? If it meets your current needs then there probably isn't a reason to increase the battery size. Otherwise, consider a battery replacement to increase battery life. Most, if not all, battery replacements will be larger to accommodate the increased capacity. It's not likely that you'll find a bigger capacity battery that is the same size as the current as the increase wouldn't be substantial.
If you don't want the added bulk consider a mobile battery pack that can charge the device on the go.