The Siphon Hose is waiting in Joel's backpack when the Pittsburgh chapter begins, so you collect it without doing anything.
Bill hands over the hose so Joel can siphon gas from vehicles on the road.
Bill gives it as he parts ways with Joel and Ellie at the end of Bill's Town, after they get a truck running with his help, so it is the last thing he does for them.
Abandon Zone Note
The Abandon Zone Note sits on the desk in the office at the far left end of the bookstore's first floor in Pittsburgh.
Accretion
Accretion, issue 6 of Savage Starlight, sits on a coffee table in a lounge on the second floor of the Hotel Grand, during the Hotel Lobby section of Pittsburgh.
Ambush Map
The Ambush Map is pinned to the wall of the room at the end of the hallway. Leave the stairs in the room with the two dead bodies, follow the corridor to its end and look on the wall.
Applicant Checklist
The Applicant Checklist is under the stairs on the far left of the bookstore's ground floor in Pittsburgh.