ND W24ES plugs are equivalent to ND B8ES. Nessim posted a link a few weeks ago to fleaBay wherein the seller is offering NOS W24ES plugs.
kzrider.com/forum/4-electrical/616014-ti...ck-up-on-spark-plugs
We bought two boxes, and compared theplugs, individual boxes and case boxes to some NOS ND W24ES plugs we've had on the shelf for many years. We're confident the fleaBay plugs are genuine.
We've run ND W24ES and W24 ES-U (U-profile ground electrode) plugs in our Z1's for decades. They run just fine.
Good Ridin'
slmjim & Z1BEBE