After playing through the DLC this is everything I found. As far as I know the only item missing is the Agony weapon but there might be more, oh and some keycards as I have lock 150 so didn’t use them. Either way hope this helps if your missing any.
The PET or P.E.T science weapon location in the Outer Worlds Peril On Gorgon. This unique weapon is found in two steps first you must collect 4 magazine issues. The magazine is called the Exhilarating Adventures of Archibald Excelsior and the location of all 4 is shown in the video