Our wiki page for dillapiole is found here: Dillapiole
I did a bit of research on this. Its very hard to get pure dillapiole at the moment if you're not a registered business.
On our wiki page just a moment ago I put several sources for dillapiole I just found out about. The best sources are Piper aduncum, and Apium nodiflorum (from Italy). Those are hard to buy.
Black caraway essential oil is relatively easy to get and it is pretty high in dillapiole. The reference I gave on our wiki page shows the amount as 44.6% in the fruit (seeds). That's pretty good. That's better than dill seed CT dillapiole at around 20%. The problem with dill seed oil is the presence of carvone which competes for CYP2C9.
Black caraway essential oil tested in that article contained dillapiole (44.6%), germacrene-beta (14.1%), nothoapiole (8.3%), and beta-selinene (6.8%), along with many other components in minor amounts. Although that reference doesn't talk about it, black caraway unfortunately also has carvone. So it suffers the same problem as dill seed oil.
Carvone can be separated out from dillapiole by fractional distillation. I have done that. Dillapiole works much better when the carvone is removed. You can take pretty large doses that way without worry of CYP2C9 being used up by carvone.