My DD2 uses Maxalt for Migraine headaches and she recently gave me several of the plastic carrying cases that the Maxalt comes in.

If you can find some of these, I think you'll find them very handy for fishing kits, a very small FAK, etc. These are molded on round side so as to fit in a pants pocket (cargo?) and look like they would be good against rain but would probably leak if held underwater.

I am incorporating them into my PSK and will post later when I've tried them out.