This page of the Little Nightmares 2 guide contains the exact location and description of all the Hats you can obtain in the Hospital.
Location: Chapter 3, in the children's room.
To get to this hat, you have to jump on the ledge located against the right wall. At the very top of it, you will find a plush head that you can put on your character.
Location: Chapter 3, in the morgue.
You will find this hat in one of the coolers – you just have to open the door and get to the content. This hat should catch your eye – it is the only thing you can pick up here.