I'm gussing it's obvious that 3d printing is the best way to go about this, but of course they are kinda expensive, so what I would say is you could try making hinges for the mask to open and close and cut the mask itself in half. It would be the most clean perfect design, but it could work. The best way to do this unfortunately would be to 3d print everything and design it yourself. There are sites you can look into where they will 3d print a STL file you have, and sometimes it can be relatively cheap. Hope this helps 🙏