In the first half 2020 I printed over 1,000 of these face mask holders and over 200 face shields. I donated them to local hospitals, nursing homes, and other places of business. These drastically reduce strain on the ears, and were very easy to use.
I would print the main structure of the face shield, and attach a soft elastic band to the back. I would then add a clear visor that would snap on to the front of the visor.