You can do it yourself--I did.  My carbine stock had a cheap canvas sling and non-inletted swivels which I junked immediately after acquiring the gun.  I simply made tapered plugs from some walnut scraps, squeezed a little Elmer's into the holes, and tapped the plugs in.  Once the glue dries you can trim off the excess with a chisel or sharp knife.  Not perfect, but unless your stock is museum quality, it's not bad.  Now if your stock has inletted swivels, it will require more work--fitting wood pieces the shape of the inletting, etc., and the result may not be to your liking.