Unless you want an aluminum one, I'd suggest you contact one of the (used) parts distributors that advertise or post stuff on this site. For example, ZBarn and Zbyter. They should be able to scrounge one up that is in decent condition and they know enough not to send you the wrong one. Since there are only two flywheels for this era of Z, you have a 50-50 chance of getting the wrong one.
So be sure you know the correct mm of the one you need if you go to a local salvage yard. You might pay a little more, but they should give you a guarantee that at least it will fit. As long as the teeth aren't all chewed up, then you should be okay. use your old one as a core.