Lectrify Battery Holder
These are fantastic battery holders! Not only do they have an on/off switch, but the holes are big for sewing with conductive thread. No more getting the needle stuck! And, bonus, they are designed to fit on Lego Bricks! Run a piece of copper tape across the Lego, add a battery holder and LED and you have a circuit! Check out Lectrify's LED and Tilt Switch too.