I got it from one of my local nurseries as a plant. I'd start there. Be sure to go to your locally owned and operated nurseries rather than the big-box home & garden centers. The big-box places are great for flats of petunias and marigolds but outside of that check your local nurseries. Ask if you don't find it. They might be able to get it for you.

It is a pretty plant for a partial shade location. And it's botanical name is Myrrhis odorata. It's helpful to have that to make sure you are asking about the right plant.

FataMorgana

Sweet cicely forms pretty colonies -- we have it along a shady fence. It's in full bloom now. I would suggest placing a Freecyle ad for this one, because anyone who has it, has a lot. Even while it's actively growing, it could probably be dug and replanted the same day with reasonable success.

Richter's has it.

I just got a plant yesterday at a local garden club sale. I think the Freecycle ad is a good idea.