Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
I found some similar ones on e-bay for my 500 they work just fine except the distance between the mounting points was about 5 mm shorter. I just fitted a shorort link bracket to make them fit - mine were branded as Hedler from a firm near Uttoxter, Staffs.
Funny you say that, as I took a screen shot of the below from David Silver last year, says aftermarket, but marked NGK, and they were red, now I can't find the red ones, only black on their website;