If you have been certain on getting all the hats possible in the game, this place may have been the most frequently missed, forgotten and probably more irritating since you have to replay the mission in Free Play.
In Episode 4 Episode 4 Chapter 4, you will come across 2 elevators that have 2 cameras on top of them.
This area is near to where you can see Obi Wan in the place he fights Stormtroopers and deactivates the Shield Generators. Pictures will be posted of a more clearer location.
You have to use R2-D2* and it will take you up to the place you want to be.
Inside there are Hat Dispensers; keep using them and you would 110% of the time get them all; along with the achievement.
Hats I was "missing" Top Hat and Leia's hair.
(I Destroyed the 2 Cameras)