Battery Issue - Shutting Off When Bumped

When playing with my PSP 3000 if I bump it or put it down on a hard surface or shake it, the device will turn off. The battery is brand new. I also used a backup battery that is also new and the same think will happen. It was suggested to clean the contacts (isopropyl alcohol to the rescue) and build a foot at the bottom of the battery to make sure the contacts stay in contact with each other. What materials would be good for building the foot out of and are there any other solutions to this issue? Thank you.