It can be found inside a computer in the caravan at the Boston Police rationing site.
McDonnallIn-game spelling: That sonovabitch Sergeant Reise caught me trying to have a look in the warehouse and that asshole actually drew his weapon on me! Look Perry, I know you two came up together and all, but I'm telling thatIn-game spelling guy is dirty and I need you to have my back on this. Those ration crates didn't just go missing on their own, and it's our job to make sure they're getting to the people who need them. Just, lean on him a bit okay? See if he'll let you into the warehouse to have a look around.