I haven't grown sweet cicely - too humid for it here in the subtropics. It can be incredibly invasive. It self-seeds all over the place. It has a long taproot, which makes it difficult to transplant.

I don't have a problem with its invasiveness either in central Texas...however, I did in Colorado near a water source for the tap root.

If you want to purchase it, try companion plants in ohio or nichols in oregon. Both are great to deal with and have comprehensive lists.

I grow Sweet Cicely in zone 5. It's not invasive for me, but it grows robustly. I collect the seeds though, so maybe that's why I don't have a problem with invasiveness. Horizon Herbs in OR might carry Sweet Cicely plants. Or WellSweep Herbs in NJ

I've had the same experience as Herbalbetty.

Richters is in Canada (not far from Toronto) and they may carry seeds/plants you seek so check them out as well.

FataMorgana