Or you could try this place which is in Ontario, so might be even cheaper than shipping from Australia
http://www.petpharm.org/index-can.htm
And if you happen to be visiting Toronto you can just walk in, as I do sometimes, it is a full service pharmacy. When I've been there people have been in to pick up their human meds. They have a lot of prescription items, like flea/heartworm treatments, and some non-prescript. You have to check on the site to see if they carry what you need.