I get my tulle from www.bbcrafts.com
, as well as walmart and hobby lobby. Right now Hobby lobby has their tulle on sale .77/yard for bolt tulle and 1.99 for the rolls (6x25). There is an awesome neon green color that I just LOVE at hobby lobby and i bought a bunch of it cuz i wanted to make a witch costume but haven't gotten around to it. I'd love to see what you come up with! are you making a tutu or a tutu dress?
Also, don't know if you're planning on doing a witch hat with it or not, but I saw some plain black witch hats at Target in the bargain bins for only $1.00. It was child sized. You could embellish the hat with your leftover tulle!