You can do what I did.  I made one on Cafe Press.  On the front is the spelled out Turbografx-16 logo with Bonk peeking out of the side and on the back is the large rectangular one that looks kinda like this
TURBO
  16
GRAFX
I got the kind that had orange sleeve cuffs and neck elastic.  It looks pretty f'n sweet.  In fact, adding to my uber-coolness factor, when I was at E3 last year, G4 showed me wearing it.  
It only cost like $15 and took about three minutes to design on Cafe Press.