I found a list of the seal specifications here:
If you're willing to put some effort in, they could be sourced individually. Unfortunately, my usual o-ring supplier has turned trade-only, otherwise I'd recommend them.
Hi Michael. Thanks for your reply. I will have a hunt round for the sizes as listed. It is a fantastic old gun, Just a shame FAS have gone and parts are hard to get. Not shooting target any longer but the pistol deserves a refurb if I can get the seals. Really appreciate your help sport.
Hi, Our gun smith says it’s unlikely but try TW Chambers or John Knibbs. Kind regards Andy.
That's my thoughts too. Shame because its a superb ( or was) target pistol. Thanks for the suggestions.