I've spent the last couple months ordering face masks from various print-on-demand sites to see which ones I liked best. In the end, I liked Society6 the best. The print quality and vibrance of the colors meets my expectations, and their shipping was the fastest of all of the shops I tested. Their customer service is also top notch, and they often run sales where the artist still receives the same commission as usual but the buyer gets a discount (by comparison, discounts for buyers come out of the artist's royalties when sites like TeePublic run sitewide sales.)
I'm starting off with all of my vintage inspired floral prints (which means your mask can match your dress, comforter, or phone case!) and I'll be adding more soon. These are intended for general public use only, and not for use in medical settings. You can read more about the masks and the legal details on Society6, here.
You can find the masks in my shop right here.