Do any dopers know of affordable UV lighting that gives out very little or no visible light?
This probably doesn’t help, but you’re most likely NOT going to find LED-based solutions that fit your requirements; although LED technology is really quite clever now, most violet LEDs still emit significantly within the visible range.
Most of the cheapest solutions emit quite a lot of violet light.
Is there a reasonably cheap filter that would remove the visible but retain the UV component?
I’m looking for something that would keep glow in the dark stars glowing indefinately, but wouldn’t otherwise effect the darkness of a room.