If you take a 9v battery apart, it has a pack of 6 (if I recall) AAAA cells inside. They run nominally at 7.2 volts to 9 volts. You have a couple options if your willing to go the homebrew route. Typically rechargeable batteries run at 1.2 volts and fresh normal ones at 1.5. Go to a junk shop and cannibalize an old radio or other device that uses 6 AA batteries or visit Frys, radio shack or someplace similar. Modern rechargeable hold a lot of power, like 2500 mah. That should at least triple if not quadruple your battery life. Visit a RC hobby shop if you need more power, they sell everything you need to build and charge your own custom battery packs. =) Feel free to message me if you need help.