Rechargable Energizer 9V battery.
Rechargable 9V Battery Charger.
LEDs pull a very small amount and take very little power to run. I've been using the same AAA batteries to run my 8 LED flashlight for over a year (since Christmas of 2007). I'm fairly certain you would have no problems running these LEDs off of a 9V battery. Plus, if you purchase a rechargable battery, you'll save money and be able to charge it every second or third time you recharge the SubC 7.2V NiMH for the Slash itself.
Just food for thought.
Cheers,
Kyle.