Do you mean Gas Fire Radiant? (the white elements that glow orange when the gas fire is alight?
try www.partsareana/glowworm.co.uk
they may well be obsolete, please don't blame your plumber they do get very fragile with age - no not the plumber the radiants! boilers should be serviced by Boiler Engineers
www.elanar.co.uk
May 2009