I know that I'm quite a bit late to the party, but I want to build upon this thread, as well.
A month ago, my battery died. Well, it didn't "die", exactly; one of the contacts tore, so the battery wasn't able to maintain a stable connection with the phone. And then I tightened a screw too tightly in attempting to troubleshoot the issue, and the screw snapped in half.
I was somehow able to unscrew the other half of the screw, but without the contact making contact with the, er, contact, the thing was useless. Luckily, however, the screws that came with an old, dismantled PlayStation Portable that I have managed to fit, so my phone's currently some sort of cross between a Droid 4 and a PSP-1001. It works, though. To be specific, I used one of the screws from the UMD drive, and I had to purchase a new battery off of Amazon.
In short, scrounge around. The screw doesn't need to be made out of any specific material; as long as you can manage to get the circular, copper ring of the battery's contact cable to make contact with the contact on the motherboard, you're golden.