That device above is a humidifier for oxygen supplies, costing under 2$.
It attaches to the green comfortable plastic mask, which is washable and reusable.
If we put a filter element in it, and stick on rubber flap exhaust valves to the cheap plastic mask, we would have a reusable comfortable respirator made from readily available gear, that comes already made in various sizes.
No medical personnel has to go without a medical grade reusable device again.
How would you do it?