In light of the replies (another one below) from the people I've contacted it seems as though stainless will have to be considered.
Tigerville... I've had the reply (below) today from your suggestion to contact Mike Peters at Polished Stainless. (He mentions Namrick whom I have already contacted and drawn a blank):
08:38 (1 hour ago)
hi , sorry but we are slowly stopping selling non stainless fastenings, we only have stainless in cycle and bsf now, mainly because of the same difficulties as you are finding now, the cost for these was nearly the same price as the stainless and we are asked for mainly stainless.
the only other people I would recommend is Namrick , although I don't think they supply cycle , only bsf.
Good luck, Mike.