On the subject of chargers, I just picked up this which I thought was interesting:

10400mAh LCD External Battery Power Bank 18650 Battery Charger Box with 2-Port 5A

Here's the thing with this: It's $22, and it takes 4 18650 batteries (the kind used for flashlights and e-cigs).

Because the batteries are replaceable and removeable, you can:

• Only bring one battery, or two, or three, depending on your needs.
• Or bring 4 batteries.
• Populate it with 3500mAh 18650 batteries like the LG MJ1 ones, totalling 14,000mAh.
• Replace batteries once they've worn out

It's just 111.5g/4oz without batteries, and batteries are roughly 50g each, so about 11oz with four batteries. So a little heavier than this thing (3oz more with the same amount of batteries/similar capacity), but provides more flexibility.