Question: where did they get the vibranium to make captain americas shield?
Answer: Wakanda

While the origin and fate of the original shield were not described in the original comics from the 1940s, the shield's fate was revealed decades later in 2001 through a retconned story. According to the tale, King T'Chaka of the African nation Wakanda met Captain America in early 1941 and gave him a second sample of vibranium, an alien metal with unique vibration absorption properties and found only in Wakanda and the Savage Land.  The new Vibranium sample was used to make Captain America's circular shield and his triangular one was retired.