I have an 81 KZ650 w a ZXXXX key code on the underside of the ignition switch
(
XXXX = a 4-digit number). The code is stamped into the switch & it's kinda hard to see.
An Ilco K14 X103 blank from the hardware store is what I'm using. Other blanks may work as well. Ilco has a handy on-line catalogue that you can peruse.
Ilco Key Systems
.
Click the PDF link there to the right of
Vehicle - Automotive (Section1)
Section 1 Page 79 shows the KA14 X103 blank.