so just in case one of your thingies get too old for use, here's a place of hope for you and your gadget: Battery Kingdom.
From your AAs and AAAs, they also have a wide variety of Li-Ions, Nickel Cadmiums and more! Whatever type, size or shape of battery you need, you're sure to find it here.
This one you have to try for yourself: The Sanyo eneloop rechargeable batteries. Works great, I promise you!
even the little round ones are available here!
Visit Battery Kingdom at the 4th Floor of Farmers Plaza mall in Cubao.