From 1930 until 1949 newspaper articles mentioned “rubber buttons”. Now I don’t think these refer to buttons such as those made by Goodyear of hard vulcanised rubber and patented in 1851. It appears they were some type of flexible rubber composition, used for utility rather fashion. The articles did not state where these buttons were made.
In 1949, unbreakable buttons for coats, trousers, etc., were being sold as a ‘disposals purchase.’ They then disappear from view, probably due to newer plastic buttons taking their place.