I made this up. Please let me know if you like it!!
Materials: Fabric (any pattern)
string, hot glue gun, AG doll, Pencil.
First, take your doll and the fabric. With a pencil, trace around your dolls mouth on the fabric. Leave a few centimeter, or half an inch of fabric excess. Make sure to trace a CIRCLE. Or OVAL. Now take your string. Wrap it around your dolls head so you can take it on and off. Take your hot glue and glue the string to the fabric. Place over your dolls head, and voila! A mask!
They have one on the American girl website too for your doll