I bought a cheap vinyl case from Pooleys which seems to handle most of the punishment I throw at it. I need a proper sized case to carry dc headset, kneeboard, pens, torch and spare pants/toothbrush/deodorant in case of unscheduled nightstop. Any spare room is taken up with food or newspaper, or scarf and gloves if it's cold (like today..brrr). I don't think it matters what size of bag you have as long as it fits where it's supposed to (ooh er). I've seen crew going to the aircraft with their headset and shades in a Tesco bag, which I think is probably a reverse-pose and therefore a tad wanky.