it is called Yupo https://yupousa.com/what-is-yupo/, about the properties: https://paintingdemos.com/painting-with-watercolors-on-yupo-paper-a-few-techniques/
searching availability here, found similar at Gerstaecker: https://www.gerstaecker.de/LANAVANGUARD-Universal-Malgrund.html
otherwise via Amazon or EBay. If imported from Blick in the US, you pay duty and tax plus shipping that at least triples the price. https://www.dickblick.com/products/yupo-watercolor-paper/