It's like this. You can make toxins out of scary easy stuff, like peach pits. The problem is you need the skills, knowledge and equipment to it SAFELY.
Yeah, you can get all sorts of nasty things from a variety of sources, and you can find info on how to make bombs (like the Anarchist's cookbook) BUT without the knowledge on how to apply that information and material properly you're more likely to kill yourself in the preparation phase than the public at large.
You can get radiological materials from some surprising locations in the home and public facilities but without specific knowledge.. you'll kill yourself. Just like all those guys who make crystal meth in their homes.
One of my co-workers was a sherrif before he got in the navy, and he said the scariest raid he did was on a Meth Lab where they stored the ether outside and it was OLD ether, that could detonate with a radical change in temperature that was only half of the normal change in a morning where they lived.