Simply load up the campaign mission 'Sin City' and proceed to the room with the giant chandelier fallen in front of you (this is after you go loud). Take out all the enemies (you will know you are in the right area because Hesh will question Riley's whereabouts).
Destroy all of the slot machines in the room by shooting their screen once each and then once you have started moving on and your team go down some stairs, you will find some more slot machines across the room and they will be the final ones you need.
I created this video to help:
Hope this helps.