Most of the chemicals you wanted were available as industrially purified products, but more than a dozen couldn't be found on the market. I could only search for wild plants and animals.
My first stop was Eldorado, an obscure small town in South America. I found a local guide and had him take me to a valley twenty kilometers away. It was said that Cliff Neck Grass grew there, from which some rare types of Pyrrolizidine Alkaloids could be extracted.
After entering the mountains, the path grew more and more remote. There were no highways, not even dirt roads, so we had to hack through the underbrush with machetes. Halfway there, we encountered the corpse of a local. It reeked horribly, its skin covered in bun-sized blisters, with sunflower-seed-sized insects crawling all over it. The body was so rotten that it was impossible to tell whether it had been a man or a woman.
The guide took one look and said the person had probably been bitten to death by insects. There were several insect nests nearby, and the insects were extremely poisonous. Multicolored bugs mixed together and poisoned large livestock that passed by, laying all kinds of eggs inside the animals' corpses. Of course, to insects, humans were large livestock too. Anyone unlucky enough to be attacked would end up like this person.
I asked what we should do if we encountered an insect nest. The guide pulled out a can of spray and tossed it to me, telling me to spray it all over myself as heavily as possible to keep the insects away.
As we continued deeper into the mountains, we stopped every so often and sprayed ourselves heavily with the repellent. It had a pungent smell, and inhaling it caused intense dizziness. I noticed that every