was looking for something like this given the iPhone’s infamous battery life and this seems to get very good reviews on Amazon and for the price seems to fit the bill exactly:

a $ 25.99 6400mAh power bank + a $ 8.99 USB travel wall charger = $ 19.49

to get this price use code 2FXJVX3A at checkout

6400mAh power bank: http://www.amazon.com/dp/B00S4Q9BX4
USB travel wall charger: http://www.amazon.com/dp/B00ITIIE2Q