Yes.  I was just thinking: some of it must surely have been 'cheap and cheerful', making its way into mail order catalogues.  I've got a few tucked away somewhere.  A lot of rayon shirts, lairy-looking shoes etc.  Probably not, as you say, specifically 'Ivy'.  We do read of course that something approximating to the style was worn by everyone from law professors down to whoever pumped their gas (or something like that).  This is part of the era of 'Mad Men', isn't it?  The other fifteen per cent must have covered the stuff they were wearing...