As of 2015, Walmart sells Junket rennet tablets in packages of 12. They can be purchased at retail locations, or online at Walmart.com for about $20.
Rennet is an enzymatic extract that is made from the stomach lining of young cows, sheep and goats. It is primarily used to curdle milk to make a variety of foods, such as ice cream, custard, cheese and other easily digested milk foods. For it to be effectively used in recipes, the pill must first be dissolved in cool water to activate the enzymes. Once fully dissolved, it can then be added to milk to thicken it.