Joann, Michaels, even Walmart, generally carry a small package of batting labeled "crib size" 45 x 60. That size will be large enough for several wall hangings depending on size. The Warm Company carries one usually around 10-12 dollars, less if you have a coupon at Joann's. You may be able to buy a smaller size of "batting by the yard" at Joann's or a quilt shop. The batting in a wall hanging just gives body to your project making it hang and look better so IMO it doesn't have to be anything special. I sometimes even piece scraps of batting to go in wall hangings.