This thread made me immediately think of my new D&D character (excuse the unfinished artwork)
I was also trying to research half masks online lol, but ran into the same problems as you. All that shows up is medical masks, etc. I basically landed on a cross between a belly dancer veil (he is a belly dancing character, like myself) and the face masks you see in anime. I actually recommend searching etsy for inspiration. They have everything from kandi to masquerade masks and it'll probably help you to find what you're looking for.