You have to play as a female character and search for Jason's cabin. Inside, Pamela's sweater lies in the middle, take it with the X button.
This is easily doable in a private match with just another player. Jason starts every time at his cabin, so tell the other player just where he has to go.
Those links below will help you to find Jason's cabin location.
https://imgur.com/a/0HzwLhttps://imgur.com/gallery/XzfIF