For what purpose? The reasons for a rifle sling are twofold: convenient carry, and tension against the body for greater shooting precision. An N-frame revolver does not need a sling for either of these purposes, since 1. you can carry it in a holster, and 2. there is no shoulder stock against which you can maintain contact with the firearm, producing a steadier hold.
A lanyard, I could see, to keep the weapon from getting away from you if it falls from your grip. But a sling? No sir, I don't see the point.