I haven't found a plastic container in a size I like to carry.

I still use altoids tins: one for a PSK, one for a FAK, and a smaller round one that contains cotton balls, a chapstick, a slender bic lighter and a spark-lite flint. Each is placed in its own zip-lock bag, and they usually ride in a canvas pouch on the shoulder strap of my briefcase. Sometimes I take them out of the pouch and stash them in separate cargo pockets for a short hike or bike ride.

There is some redundancy - the PSK also has a bic, 10 strike-anywhere matches (wrapped in plastic wrap), a spark-lite and spark-lite tinder, as well as a couple of bandaids and a small pack of antibiotic ointment, and the FAK has scalpel blade in it even though there are utility knife blades in the PSK. Both the PSK and the FAK tins are also wrapped in 6 feet each of nylon cord.

So far they have survived me getting caught out in a soaking rain without the contents getting wet. I haven't tried going for a swim in salt water with them, but I have hopes they'd be OK in that, too.