The Luger really dates back to the turn of the 20th century, and so is pre-Nazi by a few decades. They were the sidearm everyone wanted to bring back from WWI as a souvenir, and by the time WWII had started, while still in use in large numbers, they were secondary to the Walther P-38.
The Luger has a complex trigger-sear linkage that makes manufacturing expensive. It also makes them have a trigger feel that is anything but crisp as it come from the factory. They are sensitive to functioning reliably with anything other than jacketed bullets, and don't do well when dirty.
The toggle link that allows the action to lock is derived from the Borchardt pistol, and while it's ingenious, it's far too complex for economical manufacturing. The Borchardt used a large "clock spring" to return the action to battery, and has a large housing that hangs over the grip for the spring. Georg Luger refined the design to allow for a much smaller leaf spring to be used, which after the first production series was changed to a coil spring . There are a few other guns which have used a similar kind of lock, but not many. Swiss Lugers and Navy Lugers were made with 6" barrels, and a model made for artillery crews with an even longer barrel was made. None of them is inexpensive. I don't know anyone who is making them now because they just cost too much to manufacture.
Lugers were made with a slot in the backstrap to accomodate a wooden board stock using an "attaching iron", but really, only the Navy and Artillery Models were routinely issued with the stock. The Artillery Model also was issued with a high capacity "snail drum" magazine. A small number of Luger carbines were as a luxury item. Lugers were marketed very, very aggressively all over the world, and they are quite literally a little world all by themselves. There are gunsmiths like Barry Jensen of Bits of Pieces in Delta, BC, who will replace the 4" barrel with a longer, "restricted" barrel and re-register the gun. It all costs a fair amount, though.
The "knee action" works by recoil. When a cartridge is fired, as the linkage is shoved backward by the recoiling casing, the action and barrel recoil together for a very short distance, and then the recoiling action strikes a surface that allows the action to "break" at the hinge point in the center, lifting the toggle link and opening the breech. A spring closes the action again, stripping a round from the magazine. It works quite well and even a machine gun was made that used that kind of action. After the first series of Luger pistols were produced, it was noticed that the action didn't always close completely, and an "anti-bounce" lock was introduced. They're interesting guns from the early period of gun design and manufacture. Good luck with your hunt.
