Customs is usually extremely finicky with what they allow through.
While it looks like a toy it may still be seized at your expense.
At this time I also fairly certain that this item is not allowed on certain playing fields through out Canada, you may wish to consult with your local field before purchasing.
In the mean time there are other options that are located in Canada already that are better quality and more cost effective to use in the long run. Unless your dead set on having that specific grenade, if you are not then I would suggest looking into airsoft innovations line of products.
"Its only a little bit on fire"