I find mine at walmart, by the carnation milk and baking stuff, also I had ordered it from online stores the powdered one, is more economical.
and great to keep on hand, If I have any left over I put the powder in a ziploc baggie and freeze it, when I need it again I just take it out of the freezer and put it in a plastic container.
http://www.vitacost.com/Meyenberg-Kosher-Goat-Milk-Powder-with-Vitamin-D?csrc=MSNSHPB-072904000028&srccode=cii_18492716&cpncode=00-64552740-2