Well, one possibility is using something known as Fabry-Perot filter. It allows an extremely narrow frequency to pass, due to multiple reflections and interferences inside the material. Put the light source material within this filter, and you get a laser. That’s essentially the main difference between a led and a semiconductor laser. The filter makes only a narrow band of the emission be “stuck” there, creating a feedback effect that eventually tends to infinity, and a good chunk of that power passes through the filter reflectors, which are intentionally not perfect.

Other than that, I don’t think there is a filter that could be as narrow as the line emission from vapor lamps. Maybe using metamaterials, but a laser would be so much cheaper and easier. A vapor laser would certainly get the job done, but they are large and hard to maintain.

A laser, maybe, but definitely not LEDs. Vapor/gas lamps produce the narrowest frequency bands possible, because it comes from very well defined atomic transitions (Hz range). LEDs produce frequency bands with widths in the GHz/THz range, while semiconductor lasers can maybe reach KHz if they are really good. So, unfortunately, for this type of applications, vapor lamps would probably still be needed.

Source: I work with lasers and spectroscopy.

Edit: very good idea about using non-visible light!

The answer is not real. The tool, on the other hand, is called Perplexity. It “understands” your question, searches the web, and gives you a summary, citing all the relevant sources.

It takes some fiddling, but it works, and is fantastic!

Your description got my attention, so I opened the steam link to consider buying it and… Hey, it was already in my library!

Was able to get it here in Brazil

Kagi has worked REALLY well for me for all topics, but it is a paid service…

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As someone who works extensively with the spin offs instruments, I can safely say that they would be just as outraged. They are all bad quality, fail VERY frequently, and, guess what, you have to subscribe to be able to use all the features of the hardware you bought.