EasyAcc 4 x USB Output Port (05A - 2.1A) 12000mAh External battery pack - $38.99 + FS
 

EasyAcc 4 x USB Output Port 12000mAh External battery pack [amazon.com] - $38.99 + FS

USB Port 1: 5V / 2.1A <= Tablets
USB Port 2: 5V / 1.0A <= iPhone
USB Port 3: 5V / 1.3A <= Samsung
USB Port 4: 5V / 0.5A <= Other Nokia

Supply about 600%~700% of iPhone 4 battery life, or 200%~250% of Google Nexus 7 battery life.