I don't CD, but I don't think that means a ton of extra supplies except I'm assuming some kind of bag to put the dirty one(s) in. I'm not one that feels the need to carry every possible item in a diaper bag, but then again we don't leave the house for 12 hours at a time. With an infant, I'd check for space for 2 bottles, 1 toy, 1 book, a swaddle blanket, 2 burp cloths & bibs, extra pacis, 3 diapers/wipes & butt cream, changing pad, hand sanitzer. I would test bags out in person. Make sure it feels comfortable on your shoulder, not too heavy when empty, and is there at least 1 designated pocket (zippered?) for your stuff (keys, phone, wallet).
I have the Coach diaper bag that I got at the outlets for like $130. I really like it and expect it to last a really really long time, and become a work bag when its baby-bag days are over. It doubles as my purse when I'm out with DD, and I've never found it to be too small.