It seems that the Nintendo Wavebird is going the way of the Power Glove. According to Go Nintendo via Joystiq, Nintendo has ceased shipping its wireless GameCube controllers to stores. This isn't too surprising (the Wii has been out for more than a year and effectively completely replaced the GameCube), but it is disappointing. Since the Wii plays all GameCube games and includes four GameCube controller ports, the Wavebird presented a great way to play both Virtual Console and GameCube games wirelessly.
Go Nintendo claims that Nintendo is still shipping wired controllers to stores, which seems very odd. If you still want to play GameCube games without a cord, you can pick up a third-party controller like the Mad Catz GameCube Microcon or the Intec Mini Wireless Controller, though they probably won't feel as solid as the first-party Wavebird.
Currently the Wavebird is selling for at least $40 on eBay, and new ones cost about $60 from Amazon, so it doesn't seem likely we'll be getting any new Wavebirds soon. If you already have a Wavebird, take good care of it. You probably won't be able to replace it without shelling out a good chunk of cash.