lost screw for caliper on gilera runner 125cc 52plate?

whilst changing the brake pads on my gilera runner 125cc i lost the screw which holds the caliper together well it was more of a rod which holes in it. to replace this screw i have to buy a new caliper! Does anyone have any suggestions how to replace this screw without buying a new caliper?

many thanks

Keynote
August 2009