At only a couple of line widths in thickness, even "opaque" TPU is pretty translucent. I would use TPU for this application personally. It will by the most drop-safe out of all of the above materials on your list, significantly easier to print than polycarbonate, and its squishiness will probably also be a benefit when at least some of your recipients just can't resist bonking each other with their diffusers. It'll also be the most tolerant of having a not-quite-right fit between the printed piece and the flashlight head.

I would be especially mindful of how powerful the flashlights these will be attached to are. I have several reasonably pedestrian LED lights which are certainly capable of getting hot enough over time to deform TPU or PLA, and probably PETG as well. You might want to get your hands on an example of one of the lights this'll be attached to and run it for several minutes at its highest setting, then measure the temperature of the emitter head. If you guys are using some kind of military grade optical yeti-stunner, attaching a piece of plastic -- any plastic -- to the end might not be a winning plan.

I know it's generally frowned upon to be That Guy on a 3D printing forum, but also: Are you sure this is really a suitable application for 3D printing? How soon do you need these? How often? You can get commercially made slip-over traffic wand attachments for flashlights online for around $6 each, probably less if you buy in bulk. And entire ready made LED traffic wands for not much more. Unless you have a bank of printers or a very fast commercial printer, it's going to take a good couple of hours each at best to knock out a single one of these with an FDM printer. Time + filament costs may make it a better value proposition to just order a shitload of these off of Alibaba or Amazon or something.

If you really want to print them all: TPU. You won't have any layer adhesion issues and they will deform before they break.

If you want to use your printer and not buy something commercial: print a few sets of molds and cast them out of silicone. Like TPU they'll deform before they break.

But as others have said, a commercial product might make more sense...

I’m going to preface this with saying… you’re probably going to get a better product if you buy something mass produced. I would suggest asking a local uniform supply store (the same as served cops and security,) if they do discounts for bulk buys. They’ll usually have a few options for you.

The problem I see is weak layer adhesion leading to it snapping, unless you find some way to print it in a more horizontal orientation. The other issue is how long it’ll take to print (and wastage of failed prints,) vs cost of just buying.

It’s an economy of scale thing.

Okay, that said, I would recommend printing i red or safety-orange asa in spiral mode with a thicker extrusion width, or translucent petg.

(Edit: with translucent petg, you can have more perimeters and better light transmission, if you were doing more complicated geometry. Spiral/vase mode printing will give a single perimeter, with .6-.8mm are easily printable with a .4mm nozzle, 1mm might still be doable. 200% width will print nicely,)

TPU will be tougher and easier to put on… but it’s going to be more difficult to print reliably, IMO, and it’s probably going to have difficulty staying rigid at the thinness you need for being a traffic wand.

Side note from personal experience: stay away from the flashing/strobing modes while using it to direct traffic- it makes it hard to see the gestures when it’s dark, leading to confusion:) (and I’m guessing I don’t need to tell you how dumb people are…)

I’d use translucent PETG at the minimum or maybe nylon. A giant nozzle is probably the best option for this application.

Might be worth picking up a few different commercial “flashlight cones” to see what they are made of. Here is one for $5 USD on Amazon: https://a.co/d/625zSQg

Just a minor note: if you do proceed with this, consider carefully the orientation you print in. The Z-direction in FDM 3D prints is almost always the weakest, so you may get better durability by printing these lying on their sides. Worth testing, at least. (Also, everything everyone else said.)