This is the affordable water-tight container you have been looking for. In fact, here is a set of three of them: see-through (for safety) and conveniently sized. This nested set of small boxes is available in either English or German language versions. The info on the lid is integrated into the plastic (i.e. not just a sticker and so it will definitely stay on).
4 easy-to-use closure snaps; marked clearly with the words "Official Geocache"; dedicated space on lid for pertinent contact info. This set includes 3 sizes: 0.24L, 0.5L and 1.5L.