Storage Containers for Grenade Quest

[Jacqueline]

I'm doing the Grenade Quest and I'm at the part where I have to find sulfur and saltpeter in storage containers.
It seemed simple, but...

I've looked in every storage container on PR, Tortuga, and PDF. I've checked every barrel and crate I could find. If it exists, I've probably looked there. I still have 0/10 of saltpeter and sulfur.

Help is greatly appreciated to anyone could give me a hint of where sulfur or saltpeter is. I bet it's really obvious....