I use Aloksaks, they are plastic see-through bags similar to Zip-Locs but they are sturdier, and are waterproof/airproof (certified by the Navy to be waterproof to 200 feet).

I trust those for my wilderness PSK used for hiking and search & rescue operations.

If you need something stronger, I would go with Lock N' Lock containers available in various sizes. They are strong, waterproof and cheaper than Otter boxes or Pelican cases.