I believe the keys are just a safety/security device and not specially keyed. Our XR80 key worked on the neighbors XR80 and they are seperated aby at least a decade. My John Deere tractor is the same way, I thought I lost the keys and went by the dealership they tossed me one of of a box and said this will work, it did.
Looking at the parts diagrams for your bike it looks like the typical 2 wire switch. Just follow the two wires from the key switch down to where they plug in to the wiring harness. Unplug them and take a piece of wire and connect the two ends that are on the wiring harness together and I bet it will start right up.
Keep in mind I have no practical experience in hot wiring things like cars, dozers or tractor trailers so this is all theory ;)