They only can be found at the crash site (level 20 and up, entrance found at the very left of the primary game screen). The versions around the meteor replenish, the versions elsewhere don't.
Alkaline Battery (Battery) (Approx.20% of the time, you will need at least 240 (!!!) of them for finishing all quests at crash site)
Hazardous Chemicals (approx. 15%)
Oxygen tank (approx 15%)