Looking to Die in a Particular Way

[countingclocks]

I've been some form of suicidal for as long as I've been conscious and retaining memories, and I've been constantly preoccupied with finding the right way to kill myself for at least ten years now. I haven't done it yet because at my core I am a massive pussy, and also sometimes I delude myself into thinking there's anywhere to run from the situation I've been in my whole life. Deep down I've always known that either my life will remain the same, as it has for the past 21 years, or I will die. There is no other escape. Anyway! As stated before, I am a giant pussy, and I won't go through with anything if there's a decent chance of me surviving, or if the method is exceptionally messy/painful. My ideal method would be overdosing on heroin, or something adjacent to it. I live in the U.S. I can't order anything online, or at least not in any foreseeable future. I am also looking into aconitum poisoning, since I've heard that can be relatively quick.
Please PM if you know of options that aren't highly painful, and accessible without ordering online. I have money to spend, it just has to be in person.