I have had this one for over a year now, charges my S4 about 3 times. It is the size above the one OP linked.

http://smile.amazon.com/Jackery%C2%AE-Bar-Premium-Aluminum-External/dp/B00AANMVNQ/ref=pd_sim_cps_4?ie=UTF8&refRID=10YVD3VZRYDZC1K3PBB6