Shopify's locations are primarily used for stock keeping purposes. I.e. I have a warehouse in California and New York, and each has the same products in inventory. The idea behind locations is for faster fulfillment, though they're currently flawed since the location that is selected at checkout has nothing to do with what will give a customer the fastest shipping time and cheapest fulfillment cost - the location priority is set in your location settings.
If you don't have to track inventory for your suppliers, I recommend setting these up in Shopify's shipping profiles instead if they charge different prices for shipping. You can use Automate Shipping Profiles to bulk-assign products to their shipping profiles if you have a lot of products in your catalog.
If you do in fact require locations, I would reach out directly to Shopify support to see if they can add an additional location to your plan.
I hope this helps!