Not too familiar with vegetarian places, but I'm sure you can get veggie Okonomiyaki. I enjoyed the okonomiyaki that they served in the Kyoto train station (bottom floor, near the rear bus stop). There's also a good one on the top floor of the building over the South entrance of the Shinjuku station.
It might be a bit expensive without the meat, but I found a shabu shabu/sukiyaki place that I really liked in Shinjuku, called Mo Mo Paradise. It's across the street and about a block further from shinjuku station from the main Kinokuniya building. (not the one in Takashimaya)