So it sounds simple, and obvious: chloroform, duh! However, I'm reading Stephen King's Misery, and King's character Sheldon mentions how hard it is to find chloroform.

Ironically, my character needed a knocking out agent, but he's not in the medical field and doesn't know anyone in the medical field. I spoke to an X-ray tech friend of mine and my nurse sister, and both have said that chloroform is no longer readily available in drug stores, or even online. It's harder to get.

What's a simple agent that would knock someone out without doing any damage that's easily found in a drug store or supermarket?