If you walk into a store and tell them that you need ammonia for cycling a fish tank they will give you an odd look and tell you they don't have any. If you go to the cleaning supplies aisle and have a look, many of them will have it. Ammonia smells very bad but is a great grease cutting cleaning aid and is probably available in each of the stores that you visited. Until recently, ammonia was the main ingredient in window cleaners although these days it seems to be largely alcohol.
In each store it can be good to try -both- appoaches, stalking the isles where mops and brooms and cleaning things are and looking carefully and also asking humans, but being skeptical if the tell you they don't have it. We all have stories of how we found ours and we'll be interested to hear yours!
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