If you are correctly referring to the plunger in the barrel lug that secures the front of the extractor rod, then current the parts will be correct for your older revolver. The locking bolt and the bolt, you used both terms, are very different! The "bolt" is within the frame and the thumbpiece attaches to it. The plunger unser the barrel is the "locking bolt".
The part that locks the cylinder in place that is operated by the thumb piece is the bolt, the part that locks it from rotating is the cylinder stop. The parts operated by the thumb piece will interchange, the cylinder stop will not. The ones that have a screw in front of trigger guard are different than the later ones without the screw.
The early cylinder stops from guns with the screw in front of the trigger guard really need a stop from a gun of that era, The newer stops with no cylinder stop screw have a hole in them to keep the spring aligned where the earlier ones do not. The early ones have a plunger and a spring. If you try a newer style in them the plunger goes in the hole and ties it up. But, someone claims you can just fill the hole on a newer on with a piece of the right sized drill shank and use them in older models. That should probably work, but I believe you should find the era correct stop. I do not believe there is any difference between on for a K or an N frame
Jacksfirst has them, but they are actually a fitted part and you may or may not need to make adjustments
Because the OP was not educated as to the proper terminology. Everyone isn't born with all the correct terms. They have to learn them somewhere. Those who have the knowledge have a responsibility to inform those who do not. Plus, some terms matter way more than others. If I say grips instead of stocks everyone know what I mean, same with yoke instead of crane or 45 long colt. Were bolt is easily confused. A bolt can refer to many types of locking devices, in the distant past S&W could well have chosen to call the cylinder stop the bolt and the bolt the cylinder latch.
The one that gets me is those who insist that pistol only means semi autos, when tthe term pistol was around and used to refer to revolvers long before the first semi auto ever appeared
I appreciate those here who have educated me,.
A good method to learn the proper terms is to study an exploded view parts list like those used by Numrich