The Power Castle 26000 will do the job.
Michael --
That is an excellent unit. I got one for Ladyfriend to use on the Atlanta/Tokyo leg of her travels (and return). That's about 15 hours of on-plane time, and she likes to watch movies on the SP1. Given its weight, she doesn't lug it around on her in-country travels, instead leaves it at her condo to pick up for the flight home. As you know, MP4's use a lot of battery. (My other contribution is converting her Chinese DVDs to MP4 for her next trip.)
I have an Energizer 18000 that I mostly use when I'm in an all-day business meeting and not close to a wall socket. Both of those, and the connections thereto, are products of the great DIY Power Projects shortly after the SP1 release. That was when some of us relived the old adage about the pioneers taking the arrows.
Take care,
Russ