There is no modern equivalent of the Mauser C96, mechanism wise. The closest thing there is are a few match pistols(olympic class) that are visually sinilar in having their magazine infront of the trigger. And they are all .22s.
First off, the Mauser mechanism is made up of fairly complex interlocking parts. There is only a single pin used (other than the firing pin) and a single screw, which holds the grips on. Even with the most modern manufacturing methods, the cost to make the C96 mechanism today would be prohibitively expensive. People simply won't pay what it would cost to make. And, since it offers no clear advantage over other systems, the cost and complexity simply won't let it compete in today's market.
Second, since 1994, handguns that take their magazine anywhere other than through the grip frame have been classed as "assault weapons". Now, the Federal law that did that (among many other things) sunset, and went away in 2004, HOWEVER, several states passed their own state laws at the same time, (doing the same things on a state level), and those laws did NOT have a sunset provision, and are still in place.
Even the Olympic class target guns are "assualt weapons" under those laws, and are not legal to buy in several places. California is one of those places, and a few years ago, when a young gal was trying to practice for the Olympics, her state "advised" her she had to go somewhere else to shoot her "assault weapon".
The Luger mechanism has been described, fairly well, I'll just add that like the Mauser, a modern gun usuing the same system just cannot compete in the marketplace. When someone makes a gun using the toggle system, what they build IS a Luger, a complete repro, not just the toggle system. Those guns do sell, in small amounts, to people who want a Luger.
I do not agree that the Ruger .22 pistol was based on the Japanese Nambu. While there are some visual similarities (because to a point, form follows function), I have never seen anything stating Ruger used the Nambu as his design basis. I suppose it is possible, but I think it unlikely. The grip frame of the Ruger Mk series pistol is exactly the same shape as the "pistol grip" of a hand drill that Ruger was making, before they got into the firearms market.
I know another
design with a cylindrical bolt that is cocked by pulling back on the rear-mounted "ears".
That is the Auto Mag pistol, a locked breech design that has nothing else in common with the Nambu (or the Ruger) other than a cylindrical bolt and cocking "ears".
To a degree, form follows function. Parts that do similar things often look similar. Sometimes ideas are "borrowed", but other times, completely separate lines of engineering result in similar appearance.