I bought a vector power converter at target (best buys has them as well) and soldered in a cigarette lighter receptacle as well into it and use a standard Garmin 12 volt car charger that plugs into it. This way I can recharge it in the car or by the cells. The Vector is nothing more than a regulator which you can dial in what voltage you want, in the case of the Garmin I hold it at 12 volts which works great and also when charging the batteries. I use to have to drop to 6 volts for the steripen but I had bought a 1 hour charger that runs off of 12 volts now as well and charges really fast now as well. I envy you with the cell you bought, when mine ever go out, I'll probably have to get one of those instead of carrying 4 cells around. They were $40 a piece when I had bought them from Northern tool awhile back , but they stopped carrying them.

With your's I would solder a cigarette lighter in yours coming off the cell (unless it has one) and plug the vector into that and solder another cigarette lighter (in parallel with the vector lead)coming off the Vector. The vector comes with adapter tips that plug into most chargers and electronic gear. The garmin, I had to use there car adapter because I could't find the mini connector.

The reason I use 2 cigarette lighters is I use the one off the cells for heavy duty drawing devices (like a fan) then I plug the vector into it (which has 2 plugs on the output (cigarette lighter and multi tip)) then I plug the electronics into the end of the vector so it's regulated.
Examples: