The Science of Ayurveda is thousands of years old, which means that there wasn't a global food market at that time. And even more important than that, the body naturally craves what it needs seasonally. You should eat mostly the fruits and vegetables that are available locally. There are a few exceptions including foods like rice, lentils, and mung beans which are staples of the Ayurvedic Diet that you may not be able to find locally. In that case just buy the organic variety.