I picked this bag up for $49 at MicroCenter in New Jersey. It's a great compromise for size and the ability to carry more than just the iPad. I can carry my other stuff such as magazines, notebook/journal, and other accessories. Plus I can through in my Dell Hackintosh if need be.
http://www.timbuk2.com/tb2/products/laptop/laptop-messenger-style/freestyle-netbook-messenger
http://www.timbuk2.com/tb2/products/laptop/laptop-messenger-style/freestyle-netbook-messenger