My kit is kept inside a Nalgene bottle, and I have a metal cup that is designed to nestle on the end of the Nalgene too. The bottle/cup is held inside one of those neoprene bottle insulators that can be clipped on the outside of my pack (although I typically keep it inside). Contents could be dumped into the neoprene insulator sack if I needed to use the bottle as a normal bottle. You can't ask for a more waterproof place to store your kit than a Nalgene bottle. And it's easy to break or recreate the watertightness just by opening/closing the lid normally. Some kits are sealed with tape, and their waterproofness may be compromised the first time you pull that tape off and it doesn't stick as well when you reapply it.