Dr Joe Falkinham, who is viewed as the guru of NTM in water, recommends bottled spring water - it has consistently been shown in tests by his university lab to have the least NTM. He mentions a few by name, but says most should be safe, as they come right from the ground without running through a local water supply. In my travels I have found that every brand of spring water is not necessarily available nationally, so I use what I can find.
He cautions against "bottled drinking water" - which is often just local tap water with minerals added. Many of the best-known brands are just that so read the labels.
Sue