So the scientist at Forest Station is sending me on a fetch quest to get the parts for that gun. The Flux thing you can buy in the shop, that I got. The other thing I need is in a hot place he said. I assume it's either the desert or hell. I've been searching like crazy through both but am not having any luck. Help is appreciated.

btw, game is amazing.

Actually its in Desert Hell. Go to the desert and leave the town, you'll see a rock just like the one in Forest, and you can go to hell there too.

Thanks a lot. I actually looked there some, I guess not in the right place. I will continue searching!