So volunteer to put yourself around 300 potentially sick and contagious people a day for no money (and no sick pay and no responsibility if you do).
Either private companies are too expensive or even they wouldn't put their workforces at that level of risk
I went for my flu jab at the doctors on Saturday and the only person who got anywhere near me was the nurse who administered the jab, we queued outside, walked to a line, they were a good 8 feet inside and we gave our names and then were led through by the nurse herself. I can imagine you'd wear full PPE and just deal with things like telling people where to queue and pointing the direction they need to walk.
I'd also hazard a guess that they've looked at the infections among shop workers to gauge the risks, they deal will hundreds if not thousand wandering through the shop every day, not masked, touching everything in sight, not giving them any room.