The problem with otter boxes and stuff is that they have no other use except to carry your PSK. Thats why I pack mine into a soup can. I can use that can in an emergency to boil water, to carry water or to cook with. This way every part of my PSK including the container has a good use. A small coffee can with the snap on plastic lid is very useful. Just wrap tape around it a few times and it is reasonably waterproof.
The round shape dosen't fit in a pocket as comfortable as a flat tin would, but it still fits. Just like anything in life, there has to be a compromise.