ASGI do ship BB's to Canada and they fake your invoice to avoid duties and the associated brokerage fee.
I have placed multiple orders to the US and Hong Kong over the last month and not one of them incurred any extra fees at all
Beware of ASGI having items that say they are "in stock" on their site and then email you later after you've paid in full to say the item is out of stock, which is really frustrating when you order only 3 items and it takes you a whole week just to find out that two of the three items aren't in stock. Then it's another week wait to get your refund through Pay Pal.
I would never buy anything airsoft related from a Canadian retailer (other than a full metal gun) because I don't feel I should be the one to put their kids through college so the US and HK get all my gear $.