aww man, i would love to have one of those!
but i have an emulator and i use a xbox 360 controller. it works great as a n64 controller, and the wired ones have usb ports and you can install them on your computer. then you should know how to change the buttons for them.
anyway if you dont want to use the xbox controller you can find one of those on amazon/ebay (hopefully) or just look it up. i dont think anyone really makes those but good luck anyway.
wait! i found one,
http://www.amazon.com/Adapter-Nintendo-Controller-Joystick-Gamepad/dp/B003VTIGEO/ref=sr_1_7?ie=UTF8&s=videogames&qid=1283631398&sr=8-7
hope it helps
