I've got one of these on the way:
Drinksafe Travel TapSupposed to be the ants pants. Filters just about anything, and when the filter reaches end of life it stops all flow - this is apparently a failing with some filter systems.
Primarily, it's for Scotland. The water there is generally pretty good except for popular areas or if a river is 'in spate' where a lot of organic matter is carried in the water.