@Donk - Your search Fu sucks!
The ILCO long ignition blank is a
X248 YM63. Spares are good and Yamaha keys are typically on the soft side and people often crack them at the point where they fit into the gas cap and luggage locks, which is a shorter depth.
The short blank that fits the pattern,
ILCO X254
On a related note, I didn't like using the main key for the gas cap so just cut down an ILCO X248 and installed a hardware store appliance knob. The knob has a set screw, plus I used some JB Weld so it would be solid, after test fitting and being happy with the length so it was flush to the gas cap lock. Then I removed the flap on the gas cap and left the short key in all the time.
More info and pics of the knob I used for the fuel cap key
HERE.
This is the second time this week I've had to search and quote my own posts to help someone out. Slackers!