Update: My build notes at NIH:
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. A second shield is printing now.
Mirror for bed:
Shopping List for face shield components beyond the 3d printed part: