Just a suggestion based on the context.

مشعل from اشعل شيئاً يشعل شيئاً فهذا الشيئ هو مشعل
مُشعَل from set fire on or flare up something, so that flared thing is مشعل flare
عثوري from عثر على to find something, عثوري means finding or discovering and here it means to enable people to find you

"Flares are an easy, cost-effective way to increase officer safety while conducting roadside investigations."
https://www.police1.com/officer-safety/articles/if-your-agen...

There is another type with led :
Police & Emergency Service Road Flares
Highly-visible and rugged LED road flare for police and emergency service personnel
Our BEACON-4 LIFE LED flares are trusted worldwide by police, fire, and emergency services personnel — including volunteer units — to effectively light emergency scenes.
https://beacon-4-life.com/police-emergency-road-flare/

another option :
illuminating ammunition and still you can use "fire flare" but that is rare to use by police force.

flashlight
If it was written : مصباح عثوري
(pay attention the difference between مصباحj and مشعل )
then it would be : flashlight

Law Enforcement Tactical Flashlight
https://phantomlights.com › personal-lighting › law-enforcement-tactical-flashlights
Law Enforcement Tactical Flashlights - Phantom Lights
Our law enforcement tactical flashlights — Phantom Warrior TLS™ lights — offer three filterless colors in a compact, durable flashlight powered by AA batteries. We have more specific options for airborne law enforcement and ground crew as well. Shop with Phantom Lights today for police LED flashlights and more. Home. Personal Lighting.