I have recently ordered and received a new flame failure thingy for one of my SMEV burners from my local chandlery
Launceston) with no problems. A visit to a Smev stockist locally should sort it out for you, if not Tamar Marine
do mail order. A problem which you may have is rusting of the top burner plate which is not stainless. I am considering replacing all three of mine with stainless discs. So didn't bother ordering new ones as it is poor design supplying steel
discs on a boat stove anyway.
Good luck with it