[mrerick]

Most likely the dealer that sold the Luger would obtain extra magazines and tools from the manufacturer's distributor that they already had the relationship with.

Patents encumbered the designs of most firearms for the first decades of their manufacture. If an aftermarket manufacturer were to make them, they would be paying design royalties to the patent holder.

Aftermarket commercial items were unlikely, but of course possible. Some of the countries using Lugers licensed the design and had their own magazines made locally. Think of the Swiss and Dutch Lugers. Erfurt had them made for their Lugers under license, and Haenel Schmeisser made their excellent welded and milled steel magazines, which were used for some Commercial Lugers.

The earliest non DWM / Erfurt / Mauser / Krieghoff / Simson 9mm Luger magazine I own was made after WW-II. It is bright nickle plated and made by ERMA.