I wanted to do the same thing, so I stuck my head under the dash and saw a plunger type switch that is on the back side of the clutch pedal arm. When the pedal is down, it pushes the switch in, thus the ignition will work.
I plan to check the wiring to see if a jumper wire will close the curciut, but in the meantime I did what any self-respecting do-it-yerselfer would do, I wrapped it with DUCT TAPE!
It's permanently closed, then I secured the switch up out of the way of the pedals so the wires would be safe.
I find it's convienent sometimes to start the car from outside, and told myself that I'd *never* try to start it when it was in gear. You know what I did the next week, yup I tried to start it while it was in gear, DOH!
Thinking about it I'm pretty sure the jumper wire will work, it's just finding the tiny male/female connectors that's a problem.
Have fun!