You can buy plain bags in brown or white at any craft store. Then using one of the Stampin' Up wheel stamps you can quickly roll any design onto the bag. This bag I used the snowflake wheel stamp in brocade blue. I am all about the blue and brown! I love the wheel stamps because it makes stamping SO EASY!
Just remember if anyone asks you spent a fortune on the bag and it took you a LONG time to make it.