Here's another tool for you to use after the Apocalypse: the Snail Mini Dynamo LED Anti-Mosquito Flashlight. That's a long name for a short list of features, including a handcranked flashlight and alleged anti-mosquito capabilities.
Couldn't you just claim that anything has anti-mosquito qualities, and then when users don't get bitten, they'll believe mosquitoes are actually being repelled? Perhaps this Mini Dynamo is designed to do most of its mosquito repelling in the bleak midwinter.
That said, after all the batteries in the world are finally snuffed out, this $9 snail's little twin LEDs might be quite illuminating, somewhat better than cursing the darkness.