FWIW, finding a replacement unmarked correct commercial magazine with a wood bottom that would be correct for your Luger is fairly easy, especially when compared to finding a military magazine with a serial number matching a specific Luger. Should that become necessary, that is. Depends on how motivated your neighbor is in his search.
If you think that you would like to shoot the old girl then consider buying a Mec-Gar Luger/P.08 magazine as they usually work as well or better than a 100 year old mag. Cost is about $40 with tax and shipping, and are arguably the best aftermarket Luger mag you can buy. Gratuitous link provided:
https://gunmagwarehouse.com/mec-gar-...-magazine.html
If you want a correct commercial wood-bottom magazine it's probably a $150-$200 proposition. The Mec-Gar mag will usually arrive in 5 days or less.
-Bob