Hey bras are about the right shape. You could make two masks out of one bra. They come in different sizes and colors too.
Every shop I worked at that supplied spray painting masks would buy the large size and they didn’t fit me at all. Big gaps so I bought my own. Same thing with gloves. I wear medium but the shops and hell, have the stores only have large. Dangerous to have loose fitting safety gear. I used safety harnesses when going up in the air and yup, all made for fat guys.
medical masks are even more particular - the particles of virus have the potential to kill you, so proper fitting and adjustment is essential - find someone to train you. its not as simple as many think.