The DSi Sound Speaker by Datel Japan. A cheaper way for current DSi owners to experience the joy of having a ludicrously outsized DS than buying a DSi XL!

This insane accessory (which also charges your DS when plugged in) is available in Japan for ¥3,990. It appears to work only with the DSi, since the shell fits so precisely around the system. DS Lite owners will have to find some other way to artificially embiggen their systems, like a Nerf XL case.