If you live in Japan and can get to a Poke Center you just might be able to snag on of these babies.
It appears that there will be 4 different GBAs for sale at the launch in Japan. The fourth one is a special Pokemon Center edition version of the system. It appears to be a dark silver with gray buttons. It also has little Pokemon pictures flanking the words "Game Boy Advance." But why describe it to you when I can show it to you.