Uncle Mikes out of Oregon sells a clamp-on barrel band type of swivel attachment that you can order from MidwayUSA or Cabela's I believe. Measure the diameter of your magazine tube, and order the one that corresponds to that diameter. It comes with a screw swivel base for the butt stock as well.
Keep in mind, if you use a tight sling hold when you shoot, your point of impact will change from the sling tension transmitted to the barrel via the magazine tube attachment points. No problem if you're just using it as a carry sling.
Good shootin' to ya!
