Shopping cart for a SAAS

Hello fellow hackers. I've been using React and Node to develop some SAAS ideas but I have a question for which I haven't found a satisfactory answer. How do you deal with the shopping cart aspect? Do you integrate with an existing product like WooCommerce or Shopify, or develop your own? The problem with the former is that integrating with them is a pain, while the problem with the latter is that it feels like re-inventing the wheel. With so many React\Node SAAS products, there surely must be a better option\product. What are your thoughts?