Your gun is one of the very early sloping backstrap guns made from 1972-74, at which point Ruger changed it to a conventional shape. If anyone stocks grips for these it will be NOS (new old stock) and on a dusty shelf or at a gun show. A custom grip maker might make a set for you, or you might just run a wanted notice in Gun List or on a board like this. I'm sure there's a set out there but they will be hard to find at this late date.
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