Pills are no longer available. As far as I'm aware there is no current source of powder either. You can get liquid N which you drink, generally 2 bottles is recommended. You should find all the info you need in the PPH found in the resources section under the downloads heading
Why is 2 bottles recommended? I'm assuming you are referring to the 100ml bottles from D? I was going to buy just 1 bottle after reading the below from PPH
"The sterile form of this veterinary barbiturate is marketed in small, sealed 100ml bottles that are protected with a metal seal This metal cap makes tampering obvious, The Nembutal inside is a clear liquid with concentration of 60 mg/ml, Each 100m bottle has a total of 6 gm of Nembutal -
enough to provide a peaceful death".
Edit: Never mind, looked into the faq on exitinternational and I think one bottle will be enough
"In the vast majority of cases, one bottle (100ml @ 60mg/ml) of Nembutal will be satisfactory. However, there is a small group (<1%) who may exhibit a prolongued comatose phase before death (sometimes up to 24 hours). Outright 'failures' remain extremely rare"