Have a Klean Kanteen? Love it? Don't hide it inside a backpack, strap it to the outside where you can actually get to it. Made from durable leather, and laced with 72" of paracord for all your apocalyptic needs.
Survivor's Water Bottle Holster - Leslieville Flea
If the pen is truly mightier than the sword, it deserves a fitting sheath. You’ve invested in a good quality writing instrument, so protect it like you would any of your essential tools with this hand stitched pen sleeve.