a.) You can make sure that your suppliers use one service (e.g. UPS) to ship. Then you can use the UPS calculator to get shipping costs for the 2 products from one location.
b.) You can calculate shipping charges on each product and charge a flat fee for shipping.
c.) You can calculate how much shipping would cost if you are having to ship on the opposite side of the country, then add the shipping fee in the total product cost and you could promote “FREE SHIPPING”. That way you are not losing money on the order because all you are doing is adding the shipping fee to the cost of the product. Besides…we all love to see “FREE SHIPPING” when we’re shopping online.