Police hat

The Police Hat can be found by the Lone Wanderer in the Presidential Metro Line in the Broken Steel DLC. It is by a skeleton on a bench near some of the tracks. It also has 1ap

To find this is easy, after you exit Margot's control room you will see an American Flag, go that way and turn left towards the tracks, while facing the tracks make another left. Go towards the caved in part of the tracks, and near the wall you will see a skeleton with a .32 revolver, and a police hat.

There is also another one that you can get sooner, when you are walking through the hall with a few flags, and the statues of presidents. After you exit this hall immediately turn right, it is on the bench there.