You can definitely find some of them at whole foods. I get mine from Amazon. For peppermint oil I like one made by Zongle Theraputics. It is the best tasting that I have found. I use a drop or two straight up on my tongue for nausea or to just refresh my breath. I also dab it on my temples and behind my ears for headaches. You can mix it with a bit of coconut oil to make a rub for your chest.

I also like a brand called Majestic Pure. I use their lemon oil in my kitchen diffuser and when I make house cleaners.

You can get the diffuser machines and the diffuser necklaces on Amazon too. They are both relatively cheap.