There are 36 of these to find, one in each chapter.
One way of doing this is by first finding the "power brick detector" red power brick in the Ep1 Chapter: "Mos Espa Pod Race" then buying it at the Cantina for 125k studs and switching it on in the extras menu.
An easier way is to use this guide:
http://www.neoseeker.com/resourcelink.html?rlid=160186&r...It is written for the Wii version, but I used it to help me get my missing power bricks and minikits.