1. OTW idea only - external UV LED and phosphor.

2. FWIW a good efficient modern LED can produce useful light on << 30 mA.

At lower  currents 150 lumen/Watt is "easy" and > 200 is doable.

At 1 mA, 3V  power ~+ 3 mW so at 150 l/W that's about 1/2 lumen.
On a small surface that's "quite bright" and at say 10 mA is probably at or
above your requirement.

3. "All else failing"  zinc air cells can be had in very small sizes with
as good energy densities as almost any battery type.




 Russell
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