I've seen them at King ed's before - some inside, some outside where the other rocks are (I tyhink inthe cubbies near the gravel)
.... and I remember seeing something recently on craigslist.....
here's the link!
http://vancouver.en.craigslist.ca/for/848966551.html
Hope that helps!
edit: Look, I found another one!
http://vancouver.en.craigslist.ca/clt/848993377.html