You mean the kind that looks like a Russian SKS sling made of leather, or the ones that have a d-ring toward the lower end and thin straps at the ends with buckles? I've heard of both; but believe the latter is more authentic and also tougher to find. Yooper John has some nice pics on his website, just go under the 'SKS' section and look under 'Slings' (page 20). Unfortunately, not only can you not link to his pages, but the images are protected as well.
The good news is that I believe the Romanians used the same sling on their Mosin M44 carbines, so try searching on those and maybe you'll hit gold!