Curious – Why do you need 1/8 – 40 ME screws ??
Unless you are comitted to using existing tapped holes then use 5BA instead . Commonly available and nicer heads .
The 26 32 40 and 60 tpi constant pitch series threads are all Whitworth standard form .
They were ‘ proper ‘ engineering thread series but apart from 26 they were not much used except for Model Engineering work .
Lovely boxed ME tap and die sets used to be available from several suppliers including Bond’s and Tyzack .
In my early days buying catalogues was about the limit of my purchasing power and I used to look endlessly at the boxed sets and other wonderful things in the pictures .
MikeW