I used a custom cut mirror starting from 12×12 from Home Depot as the printing surface, and Simplify3d software to generate the gcode file, which set the nozzle to 210 and the bed to 60 on an Ender 3 Pro printer. Ask me if you need any help to replicate this andy@greenrobot.com. A second shield is printing now.
Mirror for bed:
https://www.homedepot.com/p/Glacier-Bay-12-in-x-12-in-Plain-Edge-Bath-Mirrors-6-Pack-81175/205513215
Shopping List for face shield components beyond the 3d printed part:
Click to Enlarge - 2 image(s)