Ask the seller to 'discount' your shipping cost, rather than to 'combine' shipping.
You don't care if you get one or several packages, what you want is a lower shipping cost.
Note that US sellers who are enrolled in the Global Shipping Program cannot both use the Program and discount shipping.
These sellers would have to send you a manually prepared invoice through Paypal. It should include the listing numbers from eBay.
If your seller is using the GSP, and is willing to consider shipping directly, she should be shipping by USPS First Class International. Many US sellers are not aware that this postal service includes Delivery Confirmation to Canada and will carry up to four pounds of product.
