I just looked at lavan's pictures and I am really impressed...I haven't tried fitting a little umbrella before.
I usually carry as little as possible, so I have a wallet (similar to Bearn size), a very thin agenda the size of a checkbook, keys in a flat pouch, a razor thin cell phone, a little bag of contact lenses stuff, and the Hermes rain protection that I actually was forced to use the other day.
I think Ninjasue has a very pretty Kelly 25 in which she can pack an unbelievable number of things.