On petsmart.com they're $14.99, on sale for $12.99. Of course, that's american, not canadian. $16.99 (assuming that's canadian) online at Big Al's. I need it for a small tank (1.5g), so I don't want to get anything stronger.
I went to the new Petsmart in the city this evening and asked if they had one, and they didn't. After explaining what I was looking for, the fish sales associate got a confused look on her face and told me that she didn't understand why there would be a heater for bettas, since bettas should be kept at room temperature (I do believe 20-22 degrees celsius is what she said, I don't know what that is in farenheit). I replied, "Well, they are tropical fish, so they should be kept around 76-82 farenheit, according to the books I've read". She didn't look impressed...