I've been thinking about adding a bit more to this thread, and with the above posters question, I think I will. So, the dimensions of the actual bag. They are roughly, 12inx9inx4in or 30cmx22cmx11cm.
Things that do not fit:
Medium to larger magazines, three ring binders, larger notebooks, laptops(unless you have a netbook or something similar) and, of course, anything else that might not line up with one or more of the above dimensions.
Given that I love this bag (and it is the bag that I fell in love with, not the movie) I have, since getting hold of an original and a repro(of the two I prefer the repro for color and bag life), found that, despite my love for it, it is less than ideally functional for my particular needs. This being the case, I changed my needs to suit the bag while I continued to look for the closest possible approximation, but with some more functionality. Below are my best finds for anyone else who is in my situation.
My criteria for this search was first and foremost, size, followed closely by shape, color and features. Size, because, though I wanted a larger bag, I wanted to maintain the lightness and the general look of the actual bag. Color, shape and features (straps, pockets, buckles etc.) are self explanatory. If you do not mind the bag being far too large to really resemble the actual bag, then this opens up a lot of options. There are numerous canvas and leather bags out there that fit the profile. Fishing bags, anglers bags, Timberland Canvas messenger and so on. So, finally, here we go, in no particular order, except for the last one.
Barbour Tarras Spring bag, Earth
Sandstorm fishing bag, Sand
Rogue Bush Sling bag, one of the lesser likenesses, as not leather trim o nthe flap, but it looks like a nice bag
FCUK Fishing bag, has faux leather and the straps seems a bit slim but worth a look
Wolsey Canvas Messenger Bag, looks very nice, but is seemingly out of production and really hard to find
Lastly, and my particular favorite, is the Ralph Lauren, Rugby Brand Canvas Messenger bag.
If you are looking for the closest possible approximation to the actual bag, but need more out of it than the bag can provide, then I hope the above little list is of help. Good luck out there and if anyone finds anything better than what I have thus far, then jump in here and let us know. Thanks.