I sell them, they cost about a dollar. In a pinch for the weekend you could probably find an m4 by 16mm screw at autozone or Lowes in stainless steel. The hardpart is eextracting the broken piece. Cut a notch in the end and use a small screwdriver to unscrew it, it is ok if you notch the shaft, a carbide blade on a dremel is perfect for this.