Can someone expain where can I use those 'Bonus Keycards'?

    So I got 3 of those and It says that I can shop with those from a raider or something liket that, so my question is where is that raider and his shop?


    Thanks for all help!:P

          Kaneki    AGmENFKm.jpg      Senpai

    At the end of missions, you have an option to get a specific item for 1 keycard and a random item for 3 keycards

    (on the screen that shows clear rank and rewards)