Joann's has a flannel with cute monsters on it.
My favorite place to go is
www.ericas.com/ Click on applique, go to children's and scroll down. Don't stop at the first monster quilt pattern, there are several. Scroll to the end. They are very nice and you get your selection very quickly.
I've done one and am getting ready to do another in a different color. I wish I could show you a picture but every time I try to attach a picture, the upload fails! Good luck!