I think either a Baby Cabas (the smaller size, which ain't exactly "baby" haha) or a Diamond Stitch tote would be perfect!
I have a Khaki Baby Cabas and it's a great slouchy bag you can just throw over your shoulder and go without giving it a second though... like DD101 said, the fact that it just has just a snap closure could be an issue, but it molds to your body when you carry it and has a zippered pouch inside, both of which ease my worry about someone running off with my stuff!
The Diamond Stitch tote has really great, durable leather and comes in two sizes (check out the Reference Library
), and that tote has a zipper that goes all the way around, which is great!
Btw, I lurk in the HIA thread (no Hermes for me hehe, only a belt and some Twilly's... I'm a Chanel girl at heart
), but I have to say, you always look gorgeous in your pics!!