I was looking into this at one point too but I chose another more peaceful method. Supposedly it grows in North America aswell as Europe. It supposedly grows by water sources. Pretty sure I've seen it growing in a marsh area by where I live. https://en.m.wikipedia.org/wiki/Conium_maculatum
Be sure to get poison hemlock, not water hemlock. Water hemlock is a miserable, painful death.
For a great deal of detail on how poison hemlock was used medicinally, consult The Old Vegetable Neurotics, by John Harley, from the 1860s. You can find the entire thing on archive.org. Roughly a quarter of the book, the first quarter, is on poison hemlock. Harley was a medical doctor who took great care to try to figure out which parts of each plant contained the desired active principles, how to to extract the necessary compounds, even going to the lengths of experimenting on himself (although he would start with a mouse and work his way up).
One of the advantages of these older medical texts is that the methods tend to be less complex than current science, not as much equipment is required, much of the source materials are acquired from nature rather than Sigma Aldrich, and so forth. In short, the techniques are more reachable for someone who doesn't work in a chemistry lab.
My guess is that you'll have to plant seeds somewhere out of the way, in the right season, and from there wait for the harvest, then extract the coniine.
I am more than a little ashamed of my plans. Dying will leave some people bereft. Not many, mind you, but it does bother me. I feel like I am letting people down.
The other side of that coin is embarrassment in that I don't have whatever it takes to go through with life. Other people have it worse than I but they somehow manage to press onward. It's part of my overall feelings of guilt about being a unlovable loser, by most yardsticks.
I am also quite uncomfortable with my looks, but I suppose anyone who saw me would hardly need me to tell them this.