There's only one brand of GameCube component: Nintendo. Xbox and PS2 components are easy to find. You should've landed them during the Suncoast and Samgoody closings this past spring! They were being sold for under $10 during the last few weeks of closing.
Try every GameStop and EB within 10 miles - any farther, and you'll just be wasting gas money. And cross your fingers, because in March, I was able to find a GCN component at EB. Since there is no database for component GCN (because it isn't order-able), they listed it as a regular A/V cord - $4.99! Other than that, I wish you luck in finding a GCN component without resorting to eBay