Pandora Battery. You can found how to make your own pandora battery, here:

Slim: YouTube - How to make a Pandora Battery [Step by Step]
Fat: YouTube - How to Hack ANY PSP and get CFW

To buy, the battery, go here: http://www.dealextreme.com/search.dx...dora%20Battery

And, just in case thoso videos, do not tell you how to make a Magic Memory Stick, go here:

YouTube - How to make a magic memorystick (WORKS WITH ALL FW NOOB FRIENDLY)