-The nose bridge wire is important for fitting it close to the face. Try to find sturdy plastic ones, like those that come on electronics, coffee bags, etc. Those can also be washed in the garment.
-Replaceable filters can be made from blue shop towels, vacuum cleaner bags, make up remover wipes, dryer sheets, or anything else that is breathable. Another layer fabric could be used as a washable filter. Find something that gets static-y and possibly give a static charge by rubbing it against something fuzzy before putting it on. At least from information available for filtration, it seems a logical step.
-Test fabric you want to use by trying to blow out a flame through it. You shouldn’t be able to.