In North America the only way to get the Wolf Link amiibo was to buy The Legend of Zelda: Twilight Princess HD for Wii U. Other territories sold it separately. Now, in preparation for The Legend of Zelda: Breath of the Wild, Nintendo of America is preparing to sell Wolf Link separately.
Why? Because you can use that amiibo in the new game, and chances are many people won’t have owned a Wii U or the Twilight Princess HD game, but will still want to use the amiibo for Breath of the Wild. Last year NOA did hint that they’d be selling it separately in the future. Well, the future is now as we are hearing the amiibo is ready to come out. It’s all a matter of timing at this point. Expect an official announcement very soon.