You can get extended laptop batteries very cheaply. My laptop has both an extended run battery and another that goes in the DVD slot. I can work for 9 hours on it on the plane. I also carry a spare main battery that I charge for longer flights or meetings.
Used laptops can be found pretty cheaply on Amazon. Get one with a solid state drive as those handle drops very well.
You can get online backup accounts to backup the key folders on the machine if it gets stolen. These are reasonable. Just hook up the laptop when you get home and it can sync overnight.
