Wearing a face mask with glasses often makes the glasses go all foggy. The design by KrwawyHegemon helped me a lot: https://www.thingiverse.com/thing:4303905
I made an OpenSCAD file to allow adjustments to fit my nose and face. (Look at variables nose_height, nose_width, clip_total_width to adjust to your face.)
With the clip the mask fits me so snugly that when inhaling the mask gets pulled directly on my nostrils and mouth, making breathing uncomfortable. For this reason I added the second version with distancer.
This design uses the bezier.scad-library by William A Adams: http://www.thingiverse.com/thing:8483