Instead of searching for a ROM, you can purchase The Legend of Zelda: Skyward Sword from the Nintendo Wii U eShop or buy a physical copy of the game. This way, you'll have a legitimate copy of the game, and you can play it on your Wii or Wii U console.
Dolphin Emulator has an extensive game compatibility list that allows you to check if a game is compatible with the emulator. You can search for The Legend of Zelda: Skyward Sword on the list to see if it's compatible.
If you're looking to play the game on Dolphin, you can consider:
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