Hasn't this thread evolved into a "how to buy drugs" thread? bcs imho I understand people want to CTB with dignity when they want to leave but I have the impression that there is a lot of discussion on trying various substances in a recreational way.
Antiemetics can usually be bought without a prescription for sea/car sickness
benzos need a prescription but btw the more recreationally you use them the more you will need to fall asleep and you are not going to CTB with benzos only, you might get very sleepy and sleep for long, but not more. The same effect (falling asleep while SN does its job) can be achieved by OTC allergy/cold medicine and by things such as the Z-substances (that need a prescription). If you start looking for F or other substances that need a special narcotics prescription you might just be complicating things.
Beta-blockers will slow the heart so much that it will eventually stop. No pain. But you need a LOT of them and sometimes they contain a mini-emetic that will make you throw up the pills.
Imho if you get a doctor's appointment and run around the block before the appointment you will have a high heart rate. And if not complain of panic attacks. In the first case you might get a b-blocker and in the second too (or a benzo).
Getting barbiturates is very difficult, because there is newer, safer medicine and they are limited to very special cases of epilepsy.
But for purposes of CTB I think BB are easier to get with an actual prescription - they are non-addictive and in fact, depending on your presentation to the doctor, you can get them prescribed to your father, who is too sick to come.
In any case, before getting your kit ready, have a chat with a doctor. Getting committed to the hospital is usually reserved for recent attempts brought in by ambulance/police. The doctor will usually ask "can you promise me you won't do it?" and "what are your plans for tomorrow, next week and next month?" (if you say I have a party next week and next month I might be starting at this new job then you are ok).
You can tell the doctor you feel like CTB and sometimes a little medicine and some chats do help and your perspective on further life might change.