@MrJones I refurbished my friend's silvrettas so I keep all the parts that can be used again, I know what the problem with your release is, I have seen it many times. I can send you the part you want treated for rust and no wear where the holes are, but you definitely need to change the spring too. Take the screw out without breaking it because you need to keep the special nut in a reusable condition (I do not have a spare) otherwise you would need to buy new release.
If you save the bolt text me to send you the part you want you would still need to buy new spring from reflex. It will only cost you €14 for the spring instead of $150 for the whole thing!
Use WD40 for a few days before attempting to unscrew the bolt,
Good luck!
Alex,