Hi Martin. I am located in Regina, SK, and recently (1.5+ years ago now) went through a search in Canada for my 150. I came across it in
http://generalaviation.ca. It was located in High River, AB (just south of Calgary) and made for a fun adventure!
You are already familiar with the usual search sites. Kijiji is a good one. COPA has their "for sale" section, but the issue with those ads is they are just like print ads - not clickable. That said, I contacted a few different owners via that site. You must be a member to access their site, or perhaps your local flight club/school will have some print copies lying around to look at. Airports are a good place to look - often there are bulletin boards with ads.
I am not familiar with any 150s for sale in my region at the moment but can keep an eye out for you.
Good luck!
Eric
