I bought the Skooba iPad messenger bag and absolutely love it.
Netbook Messenger Netbook/iPad Bag - Case
Not only does it have a iPad-sized space to hold my iPad, it also has tons of pockets and compartments and it's less bulky than a laptop size messenger bag. Love it! It's $49.99, but they have regular coupon codes for free shipping and up 25-40% off. I think you have to sign up for their newsletter to get the codes.
And no, I'm not affiliated with the company. Just posting a positive review.