Larry Dahlberg uses a spoon or anything that has a shape of interest. He has leftover epoxy from something he's working on and puts it to use. when hard he pops it out, sands any rough spots, and paints. He puts in a small piece of stainless wire for the connection, and it isn't concave. The rounded portion of the outside creates the motion. The one I saw him use was for a musky bait, so it must be tough. You probably meant a metal blade, just giving options. Baby spoon or tiny sweet n low spoon might be the right size. Cheap too.