Welding Supply shops usually have big selection of brass brazing rods. I haven’t got any small enough but Stainless Steel would also make good squib rods. My dad use to carry a piece of 1/2” brass round stock in his vest pocket. It was only about 3” long. He used it to slide down shotgun barrel to knock out stuck cases in shotgun while using handloads. It occurred enough shooting trap or he wouldn’t have carried it in his pocket.