cheaper spokes are plated, no bueno for the flame. higher end spokes are titanium, which works great for a TI pen, idk how well it'll work for a mandrel.
i just order something like this, and cut it down to size and deburr the edges. purchasing "bead mandrels" is a sure way to get hosed.
http://www.metalsdepot.com/products/...cc=%20&aident=