Ice milk has been labeled low-fat ice cream by the government in the USA. Due to this it is somewhat unclear when purchasing if it is indeed ice milk. Many companies still make "ice milk," just go to your local grocer and pick out any low-fat ice cream for a company that still produces it.
What used to be known as ice milk (less than 10% milkfat) is now called low-fat ice cream, thanks to a 1994 change in FDA rules. A brand owned by Nestle, known as Skinny Cow, is widely available: http://www.skinnycow.com/products/icecream.aspx