The sample points are 1/4" (i think) bsp 28tpi bosses. You can buy the pukka Ducati take off pipes for about a fiver a piece. JHP had some in stock last week.
When you replace the plugs, give them a good wiping of copa slip. If this wasn't done when they were last out you may hear them self destruct when unscrewing them.................. worth ordering a coupl eof new ones beforehand. Try your existing ones first, you may be lucky