Buzz's note is a paper note in the Fallout 4 add-on Nuka-World.
Location
In Nuka-Town backstage, on a shelf in the northeast corner of the room with the armor workbench and weapons workbench.
Transcript
Keep this to yourself. Found one of them Brotherhood of Steel outposts. Whole place was torn to hell. Bodies and ghoul corpses everywhere.
Found a working power armor suit just sitting in there! All we need to do is find one them glowy battery things. Think I know where I can find one.
I'm gonna need help. You in?
-Buzz