You may be able to find some on eBay or Etsy, but really if you can't take apart a GameCube controller you should re-evaluate this project. Taking apart a GameCube controller is simply 6 triwing screws. Opening a Wii is much harder than that.Quick question, does this mean like the button switches and all that jazz? If so, can you please link me to where I can get some, because I don't know how to dissect a GC controller
If you're instead referring to pushbuttons which the controller buttons will actuate, GameCube controllers don't use any, they use a silicone membrane, which can be done for a portable but most people just use tactile switches.