Have done some reading. You need a light source with appr. 465nm wavelength.
That would be violet(blue). Some grow lights are 465nm. NB Royal Blue is 440nm-450nm.
Violet would be about 405nm. 470nm is “sapphire blue”.
465nm would be close to the latter, so that’d be a nice purty blue. 
Ledengine calls it “Dental Blue” I believe
I have no idea how well they work (never had a reason to track a blood trail) but Bushnell makes the TRKR (short for tracker) series of lights. I bought one when Walmart was selling them cheap, I think mine is the 250 lumen model. There is a white LED in the center and I think three red and three blue LED’s in a ring next to the benzel. Only one color can be lit at a time. I only use mine for walks at a local nature preserve that requires a red light if you carry a flashlight.
I’m looking at the Bushnell, Gerber, Rayovac, and Primos blood lights. Amazon has a add on item light for $6.52 I will try, along with one of the Walmart lights.
Amazon Rayovac blood light. Amazon.com
Solarforce has a 450nm p60 drop in.
http://kaidomain.com/S023004-Solarforce-LC-UV-Ultra-violet-450nm-LED-Drop-in
Here’s a cheap 450nm Ultrafire on Ali. Have no idea if its any good.
https://www.aliexpress.com/item/450nm-Blue-light-Outdoor-Lighting-Flashlight-Gray/32917726196.html?
xpebbl (XP-E2 blue) search @ arrow.com
XPEBBL-L1-0000-00301 is the highest flux bin, dominant wavelenght range 465 - 485 nm.
xpgdry (XP-G3 royal blue) search @ arrow.com
Looks like very recently they got a reel of highest flux bin units, right now I see 1000 units of XPGDRY-L1-0000-00601 in stock and selling 'em by the piece. (^̮^)
Cheers ^:)
That might fit a Solarforce light like the L2 series, but I seriously doubt it’s a SF module.
First, I don’t think they’d have the nerve to call a 450nm blue LED “ultraviolet”.
Second, a simple 1-mode driver isn’t rocket-surgery, so probably is just a bunch of cheap parallelled chip-resistors.
17bux for that? Feh…
Obviously quoted the wrong source when I wrote that 465nm is violet(blue).
But then again: I’m colorblind. Awkward.
A bit like Mendel, the founder of genetic’s and very reluctant sharing his own gene pool.
Did a bit more reading: the words Coleman light keep popping up.
Where would I find a 465nm blue already mounted on a 20mm copper DTP board to fit a C8 host? How bright would a 465nm be, anyone know?
465nm is what Cree calls royal blue.
Thanks for the link. They rate it as Estimated Output @ 350mA: 575mW. I'm no expert, but what is that about....50 lumens?
Probably a good guess, maybe a little higher on DTP with a good lens. The lowest current I run one at is 700mAh and it’s behind the wide ledil CUTE pebble finish that Dale estimates to cause a ~33% optical loss and it measures 97lm in my light box.
Do keep in mind it will actually be much more power output than 97lm of white light, it can give you a headache pretty quickly. The cheap meters probably read narrow band color light lower than reality as well.
Might I suggest the royal blue XT-E. Same target wavelength as the XP-E2 but they’re designed to be extremely true to their binning. Binned into 2.5nm groups (so you can be sure that 465nm led you purchase will be almost exactly 465nm). Max drive current is spec’d at 1.5A (vs 1.0A spec for the XP-E2)!
Also the XT-E will throw better if you’re not planning to dedomed the XP-E2 (the XT-E can’t be dedomed and if you did dedome the XP-E2 it would then beat the XT-E in throw).
https://www.arrow.com/en/products/search?q=xteary&filters=In+Stock:Yes;
Closest to 465nm one seems to be the N08.
So, how is blue gonna help spot blood?
Strange.
470nm is “blue” and 450nm is “royal blue” usually.
Good info, thanks. Don't want to dedome, so maybe I'll go with an XT-E.
Thanks! They are offering right now free shipping to Canada with no order minimum. If I get the N08, then I'll have to get a star and then try and figure out how to mount the led on the star. Never did that before yet.