JHT: I would check with Mid-South Supply to see if they carry Luger magazines and failing that I would search through the Shotgun News. There are a number of people and places that advertise Luger parts.
I believe your Luger was a commercially made pistol, that is not specifically made under military contract, but you often found those commercially made pistols in the holsters of Wermacht and SS officers. The correct magazine for a commercially made Luger is most likely with a wooden magazine base and those are available. The plastic and aluminum were, I believe, military contract as neither were as fragile to wartime abuses as the wooden magazine bases were.
The magazine loader was a piece of stamped steel with a hole in one end and a place to use your thumb on the other end to depress the magazine floorplate to assist in loading. In addition to checking with the resources listed I would also research Luger, or Luger P-08 on the net to find some collector sites that might help you further. HTH. Mikey.