What you need is the little screw that holds the cable release block on to a Copal (or is it a Compur) shutter. This should elicit a response from a wider audience. I have a couple of dead shutters kicking around, and as best I can tell, the screw in question is around 1.5mm diameter. Unfortunately, I have misplaced a jeweller's screwdriver, so am unable to give you any further information.
I'm sure someone your side of the pond will have a box of dead shutters and could probably find you a replacement fairly easily.