Lets start with looking for the water with the lowest TDS levels. Your country's government sets minimum standards for all forms of water that must be met in order for it to be sold with that particular labeling on it. These standards, while not exactly the same in every country, are relatively close in most of them. Distilled is going to be the most recommended with DI not far behind, looking for a producer of either that can do it better than everyone else in your area is not really necessary as it won't make much difference after a while in the loop. I applaud your willingness to go the extra mile in your research (it's rare to see these days) but, your over thinking things a bit.