Where do you guys get the GB music player in HG/SS?
You get the GB Music Player in the Celadon Mansion, not a hard task to accomplish. However, you must first obtain all sixteen badges. Once done, then you can go to the Celadon Mansion, third floor, and you will notice a man next to the globe. From here he will provide you with the GB Music Player, an 8-bit music player of the original GS game music.
Go have fun and break out your nostalgia my friend. ;)