If I were in a hurry I'd seriously consider removing the ignition switch and taking it to a locksmith who can then make a matching key. Key blanks from Yamaha were upwards of 20 bucks apiece last time I checked. They aren't usually in stock at most dealers, and you'll generally have to order the blank then have it cut elsewhere anyway.
There was some discussion on the old site concerning alternative blanks.
Even if there is a code, ordering one could take awhile.