Junket is actually more like pudding/custard in texture, while gelatin holds a solid shape. Junket is made with milk while gelatin is made with water and is clear. Junket is sold in powder and tablets. Some stores carry it by the Jell-O and Pudding mixes. Other stores carry it by the cheesecake mixes and pie fillings. I’ve even found it in the canned fruit aisle (since Junket is often made with canned fruit). I think if you use fat-free milk the gelatin will perform like water in gelatin. But low-fat or whole milk will probably coagulate and turn/remain “gloppy”, longer, as opposed to solidifying as water does. But keep in mind that Blancmange is a gelatin dessert that is made with milk and it also solidifies into a “shape”. You might have better luck using arrowroot or cornstarch, agar, or maybe tapioca flour, if you absolutely cannot find Junket.