We've got a clear plastic water filter unit that we got at Bunnings. It has a tap at the bottom, holds about 6 litres and uses a good quality ceramic/activated charcoal filter (Stefani) in it. You can get similar units in ceramic or terracotta. The terracotta ones are good because they are slightly porous and as the water evaporates (slowly) it helps keep the water cool, but I got the plastic because it was cheaper and I can see when it needs topping up.