IF you can, get a white or bright colored one, so it stands out and no one can miss it. The bigger and more obvious, the better.

I had a "figure 8" strap on after my accident because of the broken collarbone. Was at a doctor's office, cane, strap, barely walking what with all the other injuries & breaks (sternum, ribs, pelvis), and yet STILL this well meaning idiot technician told me not to "be so down" ("be down"??? I'm concentrating on not falling over and not crying out in pain at this moment, not "being down"!!!) and then CLAPPED ME FIRMLY ON BOTH SHOULDERS AS HE LEFT THE ROOM!!!

Sling, big yellow CAUTION sign, flashing warning lights--as much as you can. Stain some gauze with red food coloring or ketchup and pin that off your shoulder--that should keep people away. Whatever it takes.