If you are really adventurous, you can use some glass from a fluorescent type blacklight tube to filter small xenon flashtubes, small halogen lamps, or 430 nM blue LEDs or heavily pulsed broadband 450 nM LEDs to a deep blue-violet that largely works as a blacklight. These light sources, especially many xenon flashtubes, have some longwave UV output and dimly visible violet, both of which work as "blacklight".
Please beware that the blacklight tubes are glass with nearly a vacuum inside, may implode with some force if broken, contain small traces of mercury, and are coated on the inside with a phosphor powder that may be toxic. One method to hack fluorescent lamps with some degree of safety (?) is to carefully remove an end cap or chew a hole into an end cap with your not-so-good pair of wire cutters. There will be a small tube in at least one end of the tube where the air was vacuumed out. You can break this tube with narrow pliers or a screwdriver to (at least usually) break the seal without imploding the tube. Afterwards, you can cut a piece of tubing off with a homebrew hot wire glass cutting device. You are advised to hack fluorescent tubes outdoors with gloves and goggles and stay upwind from the tube.
Hosfelt Electronics used to sell a 4 watt blacklight tube (F4T5BLB) which cost $2.49 and had the catalog number 10-114.
Electronic Goldmine http://www.goldmine-elec.com has these. Their catalog number for this bulb is G26020 as of 6/15/2022.
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