Actually, I'm in the process right now of doing a video tutorial for the default, magnet, and angelic versions of the Vocaloid headsets. I've made Miku's and Len's default versions, as well. For those, I just used basic foam sheeting, foam board, and poster board:
There's also a tutorial on youtube for the default headphones, that looks good:
Only things I'd advise on her version, is to use a slightly larger headband to hold the weight of the earphones. Also, I usually use craft glue for my props rather than hot glue. Holds just as well.