Honestly I'd prefer for the prize to be something more fun than another metalsi for someone who already has one, what about something that existing metalsi can use? An accessory or tool created by you to enhance the Metalsi skilled (*cough* lucky *cough*) enough to win. Those who don't have a metalsi can earn a metalsi though.
Of course ^^. Said items could also inspire new story elements or overall flexibility to Metalsi characters giving them things that they miss or things they never had the pleasure to use before becoming a Metalsi.