I read about that on our sister forum FlyerTalk a couple weeks ago. A starter pistol is probably the way to go since they are the cheapest and you won't mind if it somehow gets confiscated. Just tell them you are a track coach!
There ya go! I wish it worked with a diver knife. I actually have an old air pistol stored somewhere. I see airgun listed, I wonder if an air pistol is considered the same? Thanks for this info Gary.