Gromwell Root/Lithospermum root?

I am trying to find Gromwell Root/Lithospermum root/stoneseeds either in powder or the dried pieces, for tea making, but cannot find any results when I search with the term グロムウェル根, and there is no translation for its scientific name lithospermum that I could find. I know Koreans have Gromwell Root/Lithospermum root/stoneseeds tea products in powder and dried pieces form, but I am wondering if in Japan it is available anywhere (either a physical shop or online, either one is ok). I tried to search Japan Amazon with the terms グロムウェル根 and just in English Lithospermum root with no results.

I have to admit I have not the palest idea what this root is, but it is called Murasaki ムラサキ　or
紫　or also Shikon「シコン」（紫根）in Japanese:

https://ja.wikipedia.org/wiki/%E3%83%A0%E3%83%A9%E3%82%B5%E3%82%AD