A hundred years ago, Rigby had an aperture sight on the rear of the bolt. Parker Hale made a sight for that - I am currently trying to fit that PH cocking piece sight into a random Mauser 98 action that is set up as a 7x57 at the moment. I read, in old days, that the rifle trigger sear and the cocking piece face were bevelled so that the sight was in exactly the same place (left / right) for each shot. I have also seen pictures of screws or bolts drill and tapped into the tang of Mauser 98 - apparently then worked down to eliminate or reduce "up/down" movement of that cocking piece.
Is probably not "cool" nor "modern" looking - but it should work fine.
Should be a picture below of that Parker Hale rear aperture sight, welded or brazed to the rear end of a Mauser 98 cocking piece.
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