cortosis is incredibly brittle and rare in its pure form. even if you found some, it would only be useful against lightsabers. strengthening it with another ore would presumably just make it block lightsabers, not disable them. that's how it worked in the EU anyway
So it's less a helmet, more of a hood?
Qimir wears it like a helmet. It's like the sensory deprivation pieces Jedi use in the Temple. It falls apart in the show though, when it's struck twice with an elbow. Qimir is shown having to weld it back together later