AT AMAZON, bestsellers in Automotive. Also, power inverters.

I keep a little cigarette-lighter inverter in the car and don’t use it much, but on our last trip Helen’s cellphone died and all she had was the 110v charger in her purse. Popped the inverter in and she was charged up in a jiffy. I keep one of the bigger ones in the garage in case we need to charge electronics (laptops, etc.) in an extended power outage, but I’ve never had to do that because our power is pretty reliable. Nice to have, though. Interesting that a lot of them now come with USB outlets.