It is on a table on the second floor of the building northeast of Hawthorne Estate exterior cell. The building is used by the nearby raider encampment as their south wall. There are no stairs leading up to the building.
Sue: You know. Robbie's in the Veterans League, I'm in the auxiliary. We do bake sales and stuff, but we're the auxiliary OF the vets league.
Rebecca: So what?
Rebecca: Sue, where'd you go? You getting the whistles and pepper spray?
Sue: Anyway, I'm pretty sure it means you can't just be an auxiliary of nothin'.
Behind the scenes
The location McElroy is mentioned as sneaking down to is another word for liquor store in Massachusetts.