(Gai) Pad Gra Prau/Prao/Pow

I love a Thai dish called Pad Gra Prau at the Thai restaurant up the street from my Alma Mater. However, i have not been able to find it at any of the other Thai places that I have visited. The reason is that it seems to be called (Gai) Pad Gra Pow, apparently pronounced "Pot kapow" (according to this website) which is usually rendered something like "chicken basil" on American menus. I wanted to make some for myself. Apparently, the key ingredient is something called Holy Basil, which is a spicy basil that flavors the dish. Is there another name for this plant? Grocery stores seem to regard the term with a lack of understanding and I cannot seem to find holy basil anywhere. I may just have to grow my own...