This is easy to do if you have access to someone with a 3d printer.

the Openscad file to create this is
module bolt(){
$fn=100;
hull (){
translate([0,0,0])rotate([0,0,0])cylinder(h=1,r=1.75,$fn=6);
translate([0,0,1])rotate([0,0,0])cylinder(h=1,r1=1.25,r2=0.2);
}
}
bolt();
Openscad is free so if you know someone with a printer they can print as many of these as you need. If they don't want to do that I can e-mail you a copy of the stl file and they can just print it. (PM me your email address and I'll send it anyway).
Hope this helps
Alwyn
