There is a number of ways to making laughing gas bottles for your modifier. You can use a LEGO air tank (jet pack whatever you want to call them) and they come in multiple colors then just hook up a hose to it. Drill a hole through the floorboard and mound the other end of the hose to the engine well. Or you can disguise a capacitor for the LED’s as a Nitrous oxide bottle just paint it: blue or silver (NOS), purple (ZEX), black (Venom),gloss white (Nitrous Express). Just place your Nitrous oxide bottle in the back or in place of the passenger seat on the floor and mount on to the floorboard by drill holes two holes on each side of the bottle and wrap zip ties or twist ties through the floorboard and around the bottle, cut the excess tie off.