There are professional reweavers who can repair holes, tears, etc. Usually, they need enough original material to make the repair as undetectable as possible. I don't know their exact methods, or whether they can work with a hat. You would have to show it to them. I would check the Yellow Pages, Internet, etc., to see if I could locate one nearby. In some cases, you can do your own repairs by removing some nap with a razor blade and using the "fuzz" to fill the holes, applying a very small amount of adhesive to hold it in. Too much adhesive will show. This works best with doeskin. It does not work well with a textured cloth.