Best Replacement Battery option - iPhone 3GS

[whosthr]

Hello folks,
Battery performance on my iPhone has degraded severely recently. I need to have it on charger for most of the day to have it make through the whole day - so I am thinking of replacing the battery myself.

Do you guys have any recommendations on any batteries available in off-market? I tried searching on google, but there isn't really any consumable information available.

Thanks in advance for all help.

 

[LaunchpadBS]

I bought a 1600mah replacement battery off eBay, really easy to fit.
After a few full cycles it's only about 10% better than my old battery, which used to last me until 4pm but I bought a mobile battery pack , little plug in 1000mah battery for like £8, it takes about an hour to discharge/charge the iPhone up to 60% so thats prob a better option.