Not surprised by your story, but still curious where you live? In the US, you can buy it in bulk quantity on Amazon. Mixing it with sugar was a ton of fun when I was a kid, smoke bombs that could totally white out a large backyard.
I could easily order it from overseas online, but the consequences are pretty harsh (violates the explosives laws). Not worth it tbh.
Somewhere else I lived in Eastern Europe, it was available in shops in 100g bags for curing meat, etc, or at the garden shop in 25kg sacks as a fertiliser.