Conceivably, if you broke the key rather than lost it, you could try a Honda trick. Get a normal jey cut & keep the transponder in proximity. This works on at least the Blackbirds, but it was found that you need the key to be connected to the earth for it to work.
Then there are the Kawasakis with a remote that works by proximity. As long as you have it in your pocket, just press the starter. I read about a "lucky" guy who lost his fob in the house... He had an understanding wife. When he was unable to locate it, he ended up wheeling the bike through the house until it would start, that told him he was close.
He did find it in the end.