Depending on how much you want to spend, there are options. I have a cheap sling I use on a Rene and a Hawken. It just has a slip loop on each end. The sling is made of nylon and the loops are leather lined to prevent slipping. One end goes around the barrel and the other around the pistol grip portion of the stock.

You can pick them up at Walmart or the like and they slip off easily when not needed