tin snips work even on the most durable and thick plastic... also on thin aluminum or light gauge steel. Just use one "real" pick as a tracing template, then cut to your heart's content. Use emery or sandpaper to smooth the edges.

I like Mark's ideas of using double sided tape and punching holes to make his picks easier to hold onto. I put velcro on my picks, then wear a velcro ring around my thumb. Works, but it looks stupid and feels clumsy. Mark's ideas are both simpler. (Thanks Mark!)