The Classic Controller Pro for Wii has been available in Japan for some time already, but it's making its way to these here parts this April.
The controller looks like it came from the PS2 factory, and it won't plug directly directly into your Wii. Instead, you have to plug it into your Wii Remote, which isn't that much of a hassle. It'll ship with Monster Hunter Tri, but will also be sold separately for $20.