I stumbled upon Es Natural Mex as I was walking to another restaurant in the area and what a lovely surprise it was! This was the first place I found in Mexico City that placed a strong emphasis on organic produce, although I'm sure there are others. I picked up some of the vegan frozen meats, but I wasn't particularly impressed with the oatmeal-based milanesa (sort of like a pork chop). That said, I was impressed that a vegan milanesa existed and I think the item would be better pan fried with some sauce or veggies, instead of just eating it plain on a tortilla like I did.
My favorite item from the store were the tamales. I stopped in a couple times so I tried a few different kinds. One had just veggies (some sort of greens that I had never heard of), and the other had carrots, zucchini, and tofu). Both were very good and I liked that they were made in a banana leaf instead of a corn husk, as I think the banana leaf makes it softer. In both cases, the store heated up the tamales for me in their microwave and they had some hot sauce on hand that I could add.
I picked up some natural sesame cookies, which seem to be all over the place in the city. They are pretty average but they made a decent snack. I also picked up a couple varieties of bitter citrus fruits that I was told go well sliced in water - agreed!