You can purchase everything you need from Amazon including Korean traditional hats (God Korean hat) in the Netflix's Korean drama 'Kingdom'.
Most hats sold from Amazon will be reproductions of the Hat and made of synthetic fiber as shown above. They can be used for an event or a Halloween party. Also you can buy them for decoration purpose.
The price ranges from $40 - $150. (Within Korea, they are sold at the price range of $10 to $ 50 excluding shipping fee.)
I could not find where to buy an authentic traditional hat 'gat' today. Unfortunately, only few people have a skill to make them since there is actually no demand for 'gats'.
For hats for men in Joseon (Chosun) dynasty era, please refer to the following:
For hats for women in Joseon era, please refer to the following:
See also a special highlight video titled "Kingdom - A Worldwide Dubbing Version", a mixture of different languages in a short video released by Netflix Korea.
Note: Joseon dynasty (Chosun; 조선) was a Korean dynastic kingdom that lasted for approximately five hundreds. Joseon was founded by Lee Seong-gye in 1392 and was replaced by the Korean Empire in 1897.