Fresh Water Container for Fully Serviced Pitch

Due to health reasons, I now use Fully Serviced pitches at every opportunity. I connect up the fresh water hose to the side of a 40 litre aquaroll using a ballcock to control the flow. However, when leaving the site, I pour away at least 20 litres, unless, I have remembered to switch off the supply earlier. So I have been looking for a plastic container (jerrycan) about 20 litres, with two caps the same size as the aquaroll. One on top and one in the side. On Ebay the only ones I can see include the ballcock and range in cost from £30 - £50. Having already got the ballcock I don't want to pay that much. Can anyone kindly point me in the direction to buy just the container?