Pacific Canvas and Leather makes a nice, heavy duty reproduction of the 1907 sling if that is what you are looking for, $22.90.
I've had one for at least ten years I've used for CMP Rimfire Sporter Competition (three position stuff) and it can't be beat, for the price. There are more expensive slings out there but I don't think any are better than this one.
http://www.pacificcanvasandleather.com/product_detail.php?ItemID=50