Sorry to bump an old thread. I would suggest you to get an external battery pack. You can simply plug your phone into the device and get it to charge while on the go. It can also charge your other devices and wouldn't be a waste when you upgrade your phone.
I personally have several external battery packs of different brands. The RAVPower 3000mAh is the most tiny one I have. I can easily put it in my pocket just like a lipstick and save my phone from dying on occassions. And I have a large one of 14000mAh, also by RAVPower. I take it when out for few days' trips. It will keep my phone charged. You can check it on Amazon.