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.