Although I do not have any left, the best I found for a container was the metal "cans" that large faced altimeter displays came in that were used in the Flight Service Stations. They had a locking ring on the lid and were a perfect size for a bunch of freeze dried food, bottle of blazo, etc. never saw one open when dropped onto tundra. Now, metal five gallon cans of gas, that's another story of limited success! I always carry plastic film cannisters with about 6 feet of surveyors tape protruding through the lid, bolt or two inside for weight, for dropping notes. I have dropped all kinds of stuff related to school supplies to family's that lived where you could not land on wheels in the summer, usually using a passenger to actually drop the stuff while I drove. Once they wanted me to drop a glass art kit! I brought it back instead.
