Get an eGo (eGo, Riva, vGo etc etc). They use 510 connection, they are much smaller that they look in pictures. The
batteries last waaaayyy longer than a regular 510 battery or even a Mega 510 battery. I now prefer the eGo over the regular 510 for on the go, fits in my pocket, and I no longer have to carry a Personal Charging case. A fully charged eGo battery will last me all day. If I am chain
vaping, 4-5 hours at least.
If I had to get another ego, I would even get a Mega or XL eGo, the battery is slightly longer and it gives you even more battery life (900 mah as opposed to 650 mah).... I have also used the 510 chargers on my ego as well. All of your Atomizers/Cartomizers will work fine with the eGo as well.
You can find the ego anywhere, I got the best deal at Puresmoker. their site says its 59.99, but when you add it to the cart, it is really 49.99(They have a sale on them this month), which is a great deal....