Talk with the guy that wants food where you can sleep in the slums.
He will tell you different things including where to get a counterfeit pass, could take several in-game days since you can get only one information per day.
After that you can get 4 different counterfeits at the marketplace (the one in the slums).
Since there seems to be random chance which pass is the correct one, as well as the fact that it changes it every time you want to UNA, you should get a massage with a happy ending to reduce the stress. 😉