The easiest solution would be to get a sound card with a game port on it, and add that to the computer, and take apart a joystick or maybe one of the car racing pedal/steering setups and use the pots from it. I'm assuming you're already using the game port on the computer for a joystick. Although I don't know what's up with USB game stuff these days, it's probably taken over the old 15 pin game ports that I'm familiar with
