I'm not sure if they're still being made or have been constantly made since then, but you can actually still buy them new. How old that stock is I do not know.
I've seen officially licensed clones of 360 controllers, but I'm not sure if anything else has gotten proper "first party quality" manufacturing for more than 10 years. No weird worn out tooling repros, actual high quality stuff. For better or worse, Smash creates and endless demand for Gamecube controllers, which Nintendo seems willing to fill. Good news for me, noted GC pad enjoyer despite not really playing Smash.
I know there was either still new production or at least lots of old stock of VMUs not too long ago, maybe that counts in a way?