extended life batteries for portable DVD players
 

So last time I flew out to Vegas I rented a DVD player in the airport from that rental service they have. The guy that worked there gave me the player and told me that the battery was designed to last 8 hours, and I should have no problems on the 5 hour flight. He was right, I used it the whole time and it was fine. From looking online, I can't find any aftermarket (or offical for that matter) batteries that come even close to that life. My dad flies across the world pretty frequently for work and I would love to get him something like this for Christmas, but getting him a portable DVD player with a 3 hour battery life isn't going to help much on the 13 hour flight from NY to, say, Dubai. Anyone know what kind of batteries they use on those players you rent in the airports?

bump for the answer...

buy a whole bunch of the 3 hour batteries, genious.