You need a mortise lock set--this vendor has some decent photos.

They require a weird hole in the door, very different from a modern knob set.

Here is a link that might be useful: reproduction locksets

There is a way to retro-fit them without using the big mortise but I'm not sure how.

You'd want a lockset like this, but you must have the knobs and their square spindle with its setscrews already, because they aren't included.
Casey

Here is a link that might be useful: Spindle lock conversion