You don’t need to create a new product, you can simply set the out-of-stock product in stock.
To enable this feature, go to WooCommerce → Settings → Products → Inventory and check the Enable stock management box in the Manage stock option.
Once you do this, go to your Products section and edit the product you want to display the stock left. Then, in Product data → Inventory, check the Enable stock management at product level box in the Manage stock? option. Once you do this, enter the Stock quantity you want to display and save changes.