hey, listen, it's easy:
N - is impossible to get today. There are many offers online - which are SCAMS, do not try to buy even if the offer sounds legit!!!
Few years back, it was possible to get, but you had to travel to south america like Peru, Colombia and try to get it in some shady pharmacy and even then you would have to bribe the pharmacist. Some people spent a couple of thousand $ for the trip and bribe. However, now the world supply of N is so low, it's impossible to get.
Only people who got it [on this site], got it only from their trusted vet friend. That's basically only one industry that N is used in - veterinary. Your cat or dog can get N, but you cannot.
now, about the other one, the situation is much brighter:
SN - it's widely used on the market as a preservator for meat (E250). In many european countries you can get it just from a shop, even online from respectible amazon/ebay. I'm not sure how the situation is in the US, but it's far easier to get, and it's very cheap. You can probably get it through a friend, or from an online vendor, if it's overseas one or not. It's far less likely to be a scam. Of course do not search for "SN ctb" but just "sodium nitrite" or "e250" and the offer has to be for meat preservation purposes. If the offer sells SN to ctb - I would treat is as a scam.
Be sure to order sodium NITRITE (NaNO2), not NITRATE (NaNO3) (!). Nitrates are far less toxic, and it's easy to mix.
However, with SN be prepared to suffer for 30min from air hunger, hyperventilation, breathlessness, chest pain, cyanosis, nausea, vomiting. It WILL make you ctb, but is not nearly as peaceful as N, where you just fall asleep.
In order to minimize symptoms, I advise you take some benzodiazepines 30-60min before SN
