I am very accustomed to carrying a "murse" around. I am usually carrying a Waterfield Design Muzetto on most days. If it was thicker than 2.5 inches, I would just use it to throw my body, lens, and extra accessories in. However, it is much too narrow.
As far as camera bags, what I already own are too big for a decent street bag for a mirrorless system. My two main bags are the Crumpler 6 Million Dollar Home (older version from around 2008 or 2009) for my DSLR "day bag" and the Amazon Basic camera/laptop backpack for my "travel/vacation" bag when I want to take a variety of equipment. I use the free Nikon camera bag that came with my Nikon D300 as may extra equipment storage bag (wireless triggers, extra cables, etc.) and looks WAY too much like a camera bag to consider taking outside to walk around. I have been using a cheap Caselogic bag that holds not much more than a single lens and a few small mass accessories. Essentially, I am seeking out a day/walk-about/street bag to carry the following:
X-T10 + 27mm or 35 f/2 or 23mm
18-55 kit lens
Extra batteries (3-4)
iPad Air
Apple SD card lightning adapter
iPhone 6
iPhone/iPad charger
Wallet
Car keys
Moleskine Large (8x5 inches)
Pens
Reading glasses
Extra SD cards
A plus but not 100% necessary additional items:
Fuji charger
Water bottle
Snacks
Overall, I would like the bag to be as close to 11"x9"x4" deep. Although weight is always a consideration (not a factor ), it needs to look equally good while wearing a casual outfit or a suit and tie.