Remember, solar panels don't provide much juice per square foot. Small and light might not get the job done. And overcast days eat into there efficiency. I would look for a roll-up type panel with about 200% the capacity you think you will need. You may need to choose your shots carefully to not expend your batteries too quickly. Also, finding an adapter for LI-Ion batteries might be difficult. They require special chargers to prevent the batteries from catching fire.