You could always buy the following...
- PDP Fight Pad ( come in many character variations. Basically a Wii Classic Controller Pro that's setup like a GameCube controller)
- Hori Fight Pad (only comes in Mario, Luigi and Pikachu. Essentially the same product at PDP's)
- Hyperkin Procube (This one is a Wii U Gamepad shaped like a GameCube controller. The only thing it's missing is analog triggers. I use this controller for PC gaming and its my favorite!)
All three options will require a Magic NS or some other adapter but at least you have options.