Hi!
I'm also new to the site, I hope you get my answer.
I was hunting this seed for ages and it's impossible to get seeds of this plant.
If you find source, please let me know.
Finally I ordered a plant from Germany. It was about 20 cm when I got it and now, after a year it's 2 meters high.
This is the webpage:
Pflanzenversand Hans- Günter Röpke - Pflanzenversand Hans- Günter Röpke
You have to preorder it.
Not any certification needed inside the EU.
Best of luck to you!
Barna
Hungary