Developer Komodo may have come up with a device that could pacify these desires. With the Retro Adapter (to be distributed by Innex), you'll be able to use original NES, Super Nintendo, and Nintendo 64 controllers with Wii Virtual Console games.
The adapter itself resembles that of a Nintendo 64 console and has three female ports for each system. It connects to your Wii via an open GameCube port. What's even better, the Retro Adapter will work with both first- and third-party accessories, so that no-name Nintendo 64 controller you have laying around may just do the trick. In case you're wondering, yes, you'll be able to use an analog control on the N64 controller as well.
Innex plans on officially announcing the Komodo Retro Adapter at E3 2009. While retail availability isn't yet solidified, you should be able to grab the accessory online by mid-June for around $20.