We use Easiyo unsweetened full-fat greek yogurt, which we can make 1 litre of yogurt for about $45. The reason we use it is cost and because it's fresh and thus the good bacteria levels are supposedly higher than 'dead' pre-packaged yogurt. Easiyo have a number of organic flavour options which are a little more expensive than the regular ones. But I don't worry too much if it's not organic since it is made from NZ milk which I trust.
Maybe try your baby on some high quality greek yogurt with some fruit puree in it (the plain yogurt might be a bit sour and unpalatable otherwise). But if he/she will eat unsweetened yogurt then that's great. There are lots of good brands at any of the international stores such as CitySuper.
Just check some of the kid's yogurts carefully first, I have found many are very high in sugar and don't seem to have much in the way of nutritional value.