Strong opioids (morphine, fentanyl, heroin, pregabalin), barbiturates (pentobarbital, thiopental), benzos that can work as CNS depressants like diazepam and midazolam, anesthetics like propofol, maybe GBL/GBH if it's available or still used in your country
Every single drug that has the potential to kill you peacefully is simply regulated, it's impossible to get, you need prescriptions and sometimes you have to be a surgeon too
The only thing in common in all of these drugs is death occurring by CNS depression (sleep > deep coma > respiratory failure), they're all strong GABA agonists
Alcohol exacerbates CNS depression in opiod overdoses so it makes your chances of dying from a opiod overdose significantly higher, benzodiazepines like diazepam also exacerbate CNS depression but they're secondary agents, this doesn't apply to intravenously injected sedatives like propofol and thiopental since you lose consciousness in seconds and die in 5 minutes
So to answer your question, no, but your closest bet would be recreational
GBL/GBH
You'll be wasting your time trying to find a strong GABA agonist that is OTC or reasonably obtainable since it just doesn't exist