or even a good, genuine NGK BE8S plug to match your OK one!?
I've heard of problems with NGK but I've never found this myself having settled on B8ES running standard unleaded fuel. Also NGK are mainstream and available in most markets, Champion less so if 'stralia is anything to go by.
try small engine shops for Champion used a lot in lawn equipt etc
At the mower shop we only use NGK's and have always myself. Very rare to get a dud. Back in the "day" I used Champs and had more trouble with them!
Cheers