I saw this posting a few weeks ago on Hack-a-day:
This afternoon I attempted something similar, with a few adjustments. I cut the head off the 6inch 3/8ths bolt so that a shifter knob could be installed directly, and instead of the spring I just used a short piece of 5/8ths fuel line with a bolt fixing it to the bottom of the box.
Next to get a cheap chopping board to make the 'H' pattern and a 2nd hand game controller to wire it up...
Simon