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This time every year in the United States, stores stock up on lots of cheap items for children heading back to school. One of the items I've spotted several years running are neoprene bags for hand held electronic calculators with graphing displays. In addition to a Velcro closure, these bags typically have belt-loops and cheap carabiner clips. Once school starts, these bags can often be had for very little cost.
I have a couple and they are used for packing lenses or flashes into non-photographic bags - or hanging from my belt when I don't want to carry any photo bag. The neoprene molds itself around the contents and protects it from minor bumps and scrapes.