Hi Emmilou
I bought a ladies Camelback charm I think its a 1.5 litre, I used for the first time on the full tour of pendle I think its great, it has a sternum strap so you can get it tight on your chest without it bouncing around, The only problem is you still need to carry a bumbag with you waterproofs in etc as there is nowhere to store large things in it. but that was great on the day.
( and there are a choice of colours, pink if you prefer )