I can get it from the "regular" grocery store. But keep in mind that my grocery store has a big natural foods section, and that is where it is kept.
I don't drink coffee either but notice a bit of a caffeine "lift" when I do a coffee enema.
You may want to play it safe and do another kind of enema.
If you have leaky gut syndrome, I wouldn't do a coffee enema. It doesn't aggravate my symptoms, personally, even though I've had terrible leaky gut syndrome. But with your migraines, I wouldn't risk it. I've always been told that the coffee doesn't get into your bloodstream from your colon, but that may not be true if you have leaky gut syndrome.
With you, I would play it safe. Better to be safe than sorry.