Get yourself a nice big battery pack such as this and a 7" tablet (my personal recommendation is the Google Nexus 7). Screen power is the biggest battery draw. You can charge the Nexus 7 almost 3 full times with that battery (there are bigger ones around). Depending upon how far you are going between charging sessions and how much use of the tablet you have, you can determine the size/number of battery packs needed. I have an older version of that Newtrent battery and it is a champ. 2A output means you get the full 10W charging. Good luck.