I have one of the sandy coloured ones (lovely colour) bought off here 2nd hand. It's very robust and waterproof and I find it ideal for the sort of needs you mention - although it's smallish, it's surprising how much you can fit in. One slight niggle is that the three horizontal padded panels "collapse" the bag when it's empty so they don't stay upright when you come to put things into it; also could do with another small zipped pocket on the front, although the one on top is pretty roomy. It sits nice and snug on the back and I find it very comfortable when riding - hope this helps.
I have one of the sandy coloured ones (lovely colour) bought off here 2nd hand. It's very robust and waterproof and I find it ideal for the sort of needs you mention - although it's smallish, it's surprising how much you can fit in. One slight niggle is that the three horizontal padded panels "collapse" the bag when it's empty so they don't stay upright when you come to put things into it; also could do with another small zipped pocket on the front, although the one on top is pretty roomy. It sits nice and snug on the back and I find it very comfortable when riding - hope this helps.