Depending on the type of accessories you're powering, one of the small sealed 12V batteries used for kids' ride-on toys would be a good choice as a power source. They're small, easy to hide, and there's no chance of acid leakage or other damage that's possible with conventional lead/acid batteries. If you need more surge current, a sealed 12V like my Harley Davidson bike runs would be a good choice. I don't have hands-on experience with any of the solar chargers.
Jerry
