I take it you are dropshipping? There isn’t a way to automate this process to my understanding. Each supplier you work with is going to have its own unique shipping costs. My best suggestion would be to start a spreadsheet and go through your products to list the product and the shipping option the supplier offers along with the product cost. That way you can set up an average shipping cost to accommodate most of your products or lump all the similar products by shipping cost by using Shipping Profiles.
If there is anything else I can help you with, please let me know.
Are you dropshipping or going to ship via shipping carriers like New Zealand Post, Fastway Couriers, EasyPost & so on? If it is with shipping carriers I can suggest you with the right shipping solution. Let me know & I will be happy to help!