Its Sodium Nitrite, not nitrate. Its a chemical salt, commonly used to preserve pork and used in minimal doses for medical conditions. You can find it on Amazon if youre in the US, (not sure about availability outside of here) and I spent 10$ for more than enough to kill 10 people.
I believe the dosing is 15g in about 100ml of water.
Itll make you puke, weak, and you may end up with a headache. Youll need metoclopromide or domperidome for anti emetics to help keep it in your system. Its also failure friendly, if you get found early, there are no permanent effects (usually.)