The ZipBaby is a sweet, small bag for just the essentials.  Measuring 8" wide x 6 1/2" tall with two inside pockets and an open space, it really is when you're rolling with just what you need and no more.  Lots of ecopeeps carry these inside a bigger tote. It’s also a convertible bag that switches to a beltbag by cinching the strap to your waist size and threading it through your belt loops.  

This one is black with an accent of coordinated b&w velvet.