I have these bags in orange and purple. They are ideal for brightening up a dull rainy day.
Today I am using the orange one. It is sturdy, repels water (as you can see in the photographs), closes at the top, stands upright and holds a lot, including A4 papers and my large iPad (it has an internal iPad sleeve). Best of all, things do not all fall into a heap at the bottom so you can always find what you are looking for.
This bag is about three years old and has been used a lot. It cost £99 from Vanilla in King’s Road in London (nearest tube is Sloane Square).