As we only plan on using Phoenix for short stop overs etc so want to travel light. When we were at our local garden center / tat shop we spotted these and thought they were ideal, saves having to take the Aquaroll and gives the dogs more space in the back of the van. For £2.99 worth a try. They will hold up to 15 litres of water, but don't know if we would trust the handle that full.
I have somthing like this and it's fine. 15litres. Ours is quite a hard plastic. I bought it with thte intention of paret filling it so we had easy access to water whilst towing. Never did use it for that though.