I really think you are looking for someone with some kind of medical or biological scientific background. Not necessarily a doctor or scientist, but perhaps a lab technician, a nurse, an administrator of some kind.
I say this for two reasons:
1. Cyanide is not the easiest stuff to come by. Today you could find a chemical supplier on the internet, but in 1996 you'd have to have access to chemical suppliers and just walking in and asking for potassium cyanide would not be likely to get you it. You'd need a legitimate reason to buy it. Possibly analytical chemistry, gold refining, entomology and a few other things.
It's not the kind of thing most people would think to use to end their lives, but it's effective and very very rapid.
2. The phrase "you may use my body." Why use? Why not "dispose of" or "do with" or something like that?
Human bodies have uses, many. They may be harvested for tissue (not likely in someone who had decayed for a while and was of unknown background, not to mention poisoned), and they may be used as educational cadavers in medical schools. Parts of bodies may be preserved as anatomical specimens or prepared and photographed for medical text books. Even skeletons may be stripped and used as classroom displays.
Yes, a dead body has uses, but would this occur to most people? I don't think so. It seems the kind of thing you'd have to have some kind of biological or medical background to even think of.