try fabric.com- they have very inexpensive ribbing (sometimes $1.95)...also joannes is a good source. my mom & i bought a bunch of different colors to use making fleece socks. we found it very inexpensive....also a (recycled) ribbing from an old sweatshirt or something could be used- maybe a thrift store- where you could pick up a few shirts with the ribbing colors you need for pennies instead of dollars.