One part is on the floor in the building next to the Catch-A-Rode
Another is on a wooden plank, you can reach it by walking ontop of the building where you found the first part.
the Third is on another wooden plank, accessible by jumping up some rocks. beneath is also one of three valves in that quest where you have to turn 3 valves.
The last one is hidden inside the cockpit of the wreckage.