I don't see where you're looking for a messenger bag. I see where you're looking at backpacks.

Have you tried using a pack like you've posted the examples of? Your mileage may vary, but I've found the waist belts to be overly restrictive and cause the bag to hug so close that they're drenched with sweat on a warm day.

If I were looking for that style I'd probably stop right here: http://www.ergon-bike.com/us/en/product/bc3