It's very simple to just put up a full shield between the clerk and the customers, you don't need to strap the shield to people's faces when there's a static point of contact.
I had to go to the hospital today for a follow up X-ray after a month long life threatening illness. Every single desk and checkpoint inside either had the glass windows slightly cracked open but essentially closed, or they were draped in plastic covers. My pharmacy also did the same thing.
This has the benefit of preventing you from touching your face after touching things customers have touched.
If you're a retail worker and you haven't trained yourself to not touch your face while in work mode, I don't know what to tell you. Be better?
Or to wear protective gear that costs basically nothing. Not touching your face at all is extremely difficult where as wearing a mask is very simple. Why suggest very difficult measures when very simple ones work better.