I make my own, and I have one of the quietest bows among the guys I hunt with. I take an old fleece pant or jacket (the thicker, the better) and I cut a 2" x 2" patch. Then I use a bow press, split the string in half, insert the patch and remove the press. Then wrap the patch tightly against the string and tie down with serving in three places. I have tried a similar commercial product, fleece patch that had strips, but it was inferior. I have used this on 2 Hoyts and an Oneida Eagle. Really takes out the 'twang' sound...
Only problem....the fleece holds scent...