had a look but couldnt find anything,.i know of one way to do it which is to spray expanding foam onto wax paper, place in an object in the shape of the dish of your bowl (jam jar lid or a cut out of wood) once its dried, get the object out, carve the expanding foam to your desired look, rockoflex (dont think you have that in the states, perhaps an acrylic based grout) and then finish it with a sealer or epoxy resin perhaps. i'm not 100% on the sealing stage tbh