Originally Posted by
Sheldon Brown
Although better hardware stores will have something with the correct (M5) threading, the heads of SPD cleat screws are specially shaped to fit the cleats. You won't find them at any hardware store I know of, but any decent bike shop should be able to provide them.
Sheldon "M5" Brown
Really? They're not the standard metric 90 degree flat head? I honestly don't know but I'd be surprised if they designed in a special screw where it seems to me that a standard one would work (though I haven't looked that closely, just going from memory during installation).