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.
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.