I cannot find any katanas in the game. I have Gunrunners Arsenal DLC. And they are supposed to be there!

They ar'nt in the novac shop, the silver rush or with Coneras, when he was alive.
They ar'nt in the Gunrunners shop.

Where the hell are they?! Do they appear at some point? Do they appear at a certain level? I am level 25.
I need help here. I have a melee character. And was looking forward to having a katana.

Where are they?

Can anyone please help me?