They're metric 3mm flat heads. You can pick them up just about anywhere that sells screws. Here's a place I've ordered from before:
http://www.hexcrews.com/index.asp?Pa...TS&Category=16
Or, if you can figure out what length you need, one of us may have some we can send you for a buck to save you from having to buy a few and pay a boatload on shipping.