Is there a source in Ontario or even Canada where I could buy a Mason's Congo sansevieria?
Sorry Betty, I don't know a Canadian source, but Bob Smoley in Florida is a good USA source. He has them for $6 (USA) http://www.bobsmoleys.com/. You might try using the name S. masoniana. That's the proper name since 2000. Happy New Year
Betty feel free to message me through Gardenweb. I don't have the Sasevieria massoniana you are after but I do have several others.
I have yet to order from the US but I do buy Sansevieria form Thailand without any problems.