Help with paid maps in zombie mode (Call of Duty: Black Ops 3)

In the Black Ops series, the zombie mode is very interesting. Right now, with all 3 parts, the problem is: I can’t buy add-ons with zombie maps on Steam. And I really want to play, complete Easter eggs and open achievements. There are no keys available in the network in stores.
Maybe someone faced this problem?
I tried to download a pirate, but for me it stupidly connects with Steam and the content becomes like a license, even if you first turn it off. Files in the root folder tried to throw, does not work. I know that it works with other games and you can play pirated DLS on a license, but in CoD it's not so simple.
In 1 Black Ops, I managed to open all the maps in zombie mode a long time ago, the information was on some forum that I can no longer find. I remember exactly I was writing some commands in the console.
I just officially need everything, no mods, no pirates, so that the achievements work and you can play with other players.