Primalwear.com offers a line of non-medical masks designed for fitness. Each mask has a small, removable framework to keep the material lifted off of your face. It helps when you are breathing hard. However, the plastic frame is very flimsy. I wanted a stiffer frame, so I designed this item with more structural strength. I have had good success with PETG, but PLA would likely work fine as well. Note: this frame will only work with the "small/medium" mask size from Primal.
It will also NOT work with a standard cloth mask unless you sew small pockets into the mask.