Oh I think there is a substitute ... well at least sth that comes near for me, being an Icecream addict myself :

I puree mango or raspberry in a blender and add plain yoghurt and put this mixture into the freezer and stir it every half an hour until you have an ice-cream-like texture (I guess if you have an ice cream machine that would be better).

You can also use frozen raspberries (or other berries) or freeze fruit-puree in those ice-cube-making-thingies (whatever you call them) and mix them into yoghurt or curd to get an iced shake.