I'm going on a long flight in a week and a half, and I was wondering if there are any types of attachable batteries that I can put on my 5.5g 80GB iPod video that will add a considerable amount of battery life to it.

The flight is 12 hours each way, so obviously it won't last that long with movies playing on it.

I don't care about a price, I just need anything that will add battery life (particulary for video) to my iPod.