Thank you for asking... I have tried Eileen's, Metalsmith, Finney & Smith, Hobby Holidays and several model engineering suppliers. Where a firm offers N/S wire / rod the range often includes 1.2mm and 1.6mm, just not 1.4mm.
Unless a S-scale calculator has a funny translation algorithm, 1/16" is 1.58mm and rod / wire of that diameter is not going to fit.