Can't you go out, spend 40 dollars or so, and get a ten hour battery that charges USB devices? First thing that showed on google when I searched "USB battery": http://www.monoprice.com/Product?seq=1&format=2&p_id=9531&CAWELAID=1642113638&catargetid=320013720000011081&cadevice=c&cagpspn=pla&gclid=CK_Vj5TkyLwCFZFrfgodLHsA7QWhy can't the slim Vita have a user replaceable battery? That was one of the great features of the PSP. You could go out and spend 40 dollars or so and get a ten hour battery. For the same price as the original Vita all I would get, excluding the included memory card, is slightly better battery life and a bit lighter unit.
Not only will it charge your Vita, but practically every other mobile device.