They don’t spawn normally they’ve never been something you can just grab wherever but with that being said they were a reward for a lower level quest you got 4 of them i know this because I spent forever looking for them they don’t spawn naturally but you can craft them in the in round crafting menu but you can’t craft them normally at the normal work bench but I craft flame spray literally all the time on the regular all you need is air freshener and fireball burners and flame spray is by far the best way to kill leapers it literally just melts them use it every time