this sort of face shield is useful in clinical situations where the wearer is protected from patients who may cough or sneeze right in their face. for going to the shop what you need is an N95 or just mouth/nose covering mask/scarf.
Might be useful for the shop clerk though, who is seeing a hundred people in a row.
Plenty of essential public areas are building plastic drapes. That’s effectively the same thing but likely cheaper and not depriving medical professionals of anything.
here in the UK they are introducing plastic shields between checkout operators and customers. largely the same and saves staff from needing to wear PPE