As I recall the VB used 6 AA batteries, correct? well the problem is that they can be running in parallel, in series, or both lol. If you can figure out the voltage that the vb requires (I dunnow hat it is since I don't have mine anymore T.T) I could probably help you. If it's not listed on the vb itself, it might be in the manual. if that's not the case, you may have to find someone who has one and get them to test the voltage for you.
A good start though would be to go down to radio shack and get enough battery pack things for 6 AA battieries (or more if you wanted to build a longer lasting battery pack lol).
so you're sure there's nothing stepping down the voltage or anything in there?
; I could have sworn I looked at a snes power adaptor recently... and uh it was a voltage you couldn't achieve with a combination of AA batteries (though I could be making that up) You might want to confirm that before you go just connecting a bunch of batteries to your now difficult to obtain prize, or connecting a power cord directly to it.