I bought a set for my Security Six stainless 6" a while back - they are fantastic, best "target" grips I've handled in a long time. With an FFL discount price drops to $34.00 or $44.00, depending on which one you buy - really not sure of the difference between the two.
https://www.gunpartscorp.com/gun-manufacturer/ruger/revolvers-ruger/security-6?page=3
If an aftermarket maker were selling these I'd bet they'd be about $75.00 easy. Nice to snag a deal once in a while.