Perola's in Kensington carries it. There's likely other locations in Kensington that also carry it.
For anyone interested we've had great success growing Mexican Oregano ourselves. Richter's has little plantlets in the spring and we just plant them in individual pots. It likes full sun. We usually are able to grow enough to last us the whole year with two plants.
247 Augusta Ave, Toronto, ON M5T, CA