Norman T300 valve Springs

Good Morning 

I may have asked this a while ago, apologies if I have. 
im restoring a Greens Master 26 fitted with a Norman T300 flat twin engine ( I know it's actually an opposed twin) obviously there are very few spares around for this engine but I need valve springs. Does anybody have knowledge of a small manufacture of valve springs that might have the size  I need or could make them? Phillip, the Norman marquee specialist doesn't have any by the way. Thanks