I watched a neat mini documentary about the use of skate helmets by specops all over the world because apparently skaters had engineered exactly what they needed in a lightweight form factor, but reasonably durable albeit disposable head protection that they could also fit other things like headsets/earpro, NVG etc. without modification like the regular general issue helmets of their branches that required cutting away of parts of the shell.

Eventually they began basically just copying the skateboard design and doing various mission specific tweaks and variants which still all share the basically perfected shape of the skater helmet.

Turns out there is not much better you can engineer something after a bunch of adrenaline junkies spent 40 years fucking fighting gravity and hurling themselves from obscene heights at pavement and plywood for fun and making sure they don't die quite as often doing it.

Has to be light, sleek, enough to save your skull from a fatal impact, and can be cheap because it's only gonna work once anyway. It's not going to stop a bullet, but it might stop a ricochet or any number of things that can still kill you.