You have to get the seeds when the pods split open in late summer/early fall. May be a bit late for that this year unless somebody has seeds in store they could send you.

You might try a PM to Siris - I'm pretty sure she has done quite a lot of cross breeding with them.

you can certainly buy them commercially and they will have phytosanitary certificates for posting to Greece..

Hi Bik, glad to see you again.
I think that the best person on this site who breeds hemerocallis is Wylie in Azores. He buys internationally and could point you in the right direction.
He just posted few days ago so go to the following link and send him a private message. Good luck.

https://www.growsonyou.com/photo/slideshow/354833-daylily-divine-light/member/wylieintheazores