A could weeks ago, I had a typical Maggie-in-the-city day. (Oooh. Maggie-in-the-City would be a good blog title.) By that I mean, I had to go to several different events/locations in the course of one day, and never once be able to pop back home to change. I went from Mass to errands in GTown to a bridal shower out in McLean. I had to carry a gift for the shower (a book), an extra pair of shoes, a paella pan which was then switched with 5 champagne coupes, which I really didn't want to break.
I found mine in a shop in Napa, but they are available online: Brook Farm General Store has the standard double-handle variety (pictured), $40; Olive and Branch has several variations, including the two handle one I have, $32. Even Etsy has a few varieties (my favorites: 1, 2). I highly recommend the version with the long handle--it is by far the best and more versatile.
And they've been making the rounds in the blogsphere: Coco+Kelly and Design*Sponge both recently featured these bags. But I'd like it to be noted that: I've carried these things for years.