I don't think there is any thing "special" about the screws.
They are 1 1/4" long and made of nylon plastic, but I'm not sure what the thread size is.
I know that you can buy them @ Home Depot or Lows, although the ones they sell are white, not black.
I guess you could use standard stainless ones, but I think (not sure) that the nut they screw into is plastic also so you want to make sure you don't over tighten and strip the threads or break something.
Hope this helps and let me know if you need more information.