i don't own a benelli, but i thought a standard sling would run from that goofy sling anchor on the right side of the stock to the forend.
you could probably try a three point combat sling as well. some of the combat slings loop around the rear end of the buttstock and connect to a sling swivel at the forend. they're kind of nice because you can shoot with the gun slung on your body, but they're usually not very wide, so it might cut into your shoulder.