Most (if not all) of those WWII "Leicas" (and sometimes "Contaxes") are just fakes made in Russia by skilled craftsmen after the SU fall.
There are some details to watch which will tell you that´s not the real thing.
If the real cameras do exist today, it´s price will be damn high, and for sure they won´t be advertised in *bay.
The real WWII Contax and Leica cameras were only marked with and P.O. number, but unfortunately it seems that there is no documentation available to check about serial numbers or whatever.
Some real german WWII cameras seem to be surfaced but there is still some doubt about their authenticity.
Regarding the cameras you mention, be sure there is nothing new under the sun today, they surely are either a Fed or a Zorki.
I guess it´s better if you look for some real FED or Zorki. Price will be lower, and surely you´ll get a decent camera, not a fake.
Ernesto