The Greek Shop in SC also does wonderful custom-made letter shirts and bags. I had a custom Mickey Mouse O Phi A bag made a few years ago and it's still going (after 6 years). For the pattern, try Wal-Mart. That's were I got my Mickey pattern from and they have a lot of other character patterns. And it doesn't have to be from fabric. Mickey came from a pair of boy's boxers!
www.greekshop1.com