My Canadian outfitter is the one who told me to buy a ThermoCell before getting into camp. Before that I didn't even know what it was. When crossing the border from Maine, I have never been asked if I had a ThermoCell and they knew I was entering the country to hunt bear. I'm sure that they are legal in Canada.
You can normally by ThermoCells and related supplies on Ebay for less money. I did.
Seeing that I don't really like thousands of biting insects, I also bought a full bug suit. Either or both are essential for spring bear hunting.