This item can be found in Trapper Town in Klamath, in the car above the fence, which can be reached by navigating the Rat Caves. However, the car can also be reached by simply clicking on it from the main part of Trapper Town as when you do so, the character will run off screen and end up in the area of the car. It will automatically be placed into your inventory when you click on the vehicle it's inside. Retrieving the fuel cell regulator also awards 200 XP, although this is not mentioned when you pick up fuel cell regulator. it can be installed by Smitty.