I have a couple of these. I have no memory of what I
payed for them, probably not very much. For those not
familiar with them Luc shutters are simple shutters that fit
on the front of a barrel lens. I suspect that you could
refasten the pin with super-glue. Another possiblility is to
simply stake the pin in place using a small pin punch.
   Otherwise try someone like Steve Grimes shop. I suspect
their labor charge would be more than the shutter is worth.
http://www.skgrimes.com