You should be able to legally buy magicians flash powder and flash paper without any fuss.
At least I can here in Germany.
Bought some on-line a while ago with some experiments in mind with remote ignition using my left over Glow Plugs. Long since redundant!! I also have Gisela's cast off Russell Hobbs toaster to dismantle for the nichrome wire.
Try searching Magicians Supplies or Flash Paper.🤞
Cheers, Doug 😎
PS It don't woik if it gets damp!!🤔