if you mean Vancouver, British Columbia..
then you can go to Big Al's in Coquitlam or the one in Richmond. They almost always carry them. But their costly... 4.99 each or 4.49 when you buy 3 or more...
Only worthwhile if you have a small tank where it won't cost you an arm and a leg to stock enough of them to make a dent in the hair algae.
The Richmond location is on No. 3 rd. across from Lansdowne Mall. And the Coquitlam one is on North Road, just a block south from the intersection of North rd. and Lougheed Hwy... located in a large plaza.