My girl Grace gave me this amazing necklace (after a whole evening of begging and flattery, but it was worth it). Although there's no actual markings that would affiliate the accessory with Nintendo out right, it's pretty obvious none the less. It says "Play Me" above the A and B buttons and it's made by a company called White Trash Charms. If you live in or near Philadelphia, you can pick it up at the Ubiq store.
UPDATE: Thanks to everyone who sent in the link for the necklace. The entry has been edited above. You guys rock!