I have never needed one on a daily basis. Phone in my pocket and wallet in my other pocket and I'm all good 
I usually carry a Day Pack with me where ever I go. I tend to keep alot of my portable computer stuff in it; mostly, jump drives, a portable usb hd, my mighty mouse, and my MBP.
This is what I carry:
Mountainsmith Day
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Cool, another Mountainsmith user. I think the Relay I have is the last large bag they every made. If they'd make one that would fit a modern MBP, I'd be all over that.
I carry a manbag/murse/satchel from H&M when I go downtown Chicago. That's about it. I've had it for three years now.
It did't have a specific model name. H&M is really generic with their stuff. It's a couple inches wider than a 13" macbook pro. So my old white MacBook fits perfectly.Do you know what model that is? Looks like the perfect size for an iPad or 11" MBA.