I'm going to guess a bit that your regular battery will run your camera about an hour. So lets say 7.5 watts. I think if you used a 4 amp hour 12 volt SLA battery and a 15 watt solar panel (
15 Watt, 12 Volt Solar Panel) you could then use a little regulator like this to feed your camera.
(**broken link removed**).
This should give you 2 or 3 hours on battery only, all day with sunshine, and somewhere in between with partly cloudy days. Few pounds to carry around though.
Let us know if this sound feasable to you and we can hooker up.