R-02 Research Facility: Endurance Location
R-03 Mile High: Endurance Location
R-04 Hostile Takeover: Endurance Location
Before you get on the freight elevators. Take out the enemies however you wish to do so then look at the vent at the end of the hallway. Jump up to it and slash away at it to reveal a chest that contains the endurance enhancement.
R-05 Escape From Denver: Endurance Location
R-07 Assassination Attempt: Endurance Location
When you make it inside the hanger go all the way to the other end and on the right side of the plane towards the wall. You will see some crates you can jump on. Jump on them and dash across to find a chest that contains the endurance enhancement.