“IIRC calcium hypochlorite needs to be stored carefully....”
Correct. Figured it was ok in its rubbering packaging...chewed right through it in my attic. Pain to clean up, but thankfully no major damage. Maybe the stuff will do better stored in glass jars, but not sure.
It will be fine in glass. However, be cautious of those jars with metal lids - the metal will rust, even behind the plastic seal on the inside of the lid.