3GS battery case recommendations

I am looking for a case that has a built in battery for a 3GS. Something similar to the mophie case, but includes the apple connector. I don't really want to mess with multiple connectors and etc. I have had bad issues with 1 iPhones in the past year. They were bought on eBay and were in decent shape. First was ourchased last September and arrived with a random battery dyiny, and taking a while to come back on. Battery was replaced in October and lasted until early May. The battery ended up swelling and may have damaged the board since the camera did not work, nor did cleaning contact, or new camera. New phone was bought in early july and is working fine, but I would like to have a portable battery or a case with a battery. I have found some items that would be perfect, but not sure of the sites they are on. Thanks for any help.

Products,

http://www.cellularoutfitter.com/p-116559-apple-iphone-3g-3g-s-solar-battery-pac k-case-black-1600-mah-.html?source=gbase&gclid=CMCj3rq1y7gCFfFDMgodHksAxQ