How to display most frequently bought products at checkout?

[ivakaraivanska]

We are trying to show the customer the most frequently bought together products on the checkout. I have implemented the example from Shopify docs  but in this example we are fetching the first 5 products and we don't need that functionality we would like to fetch the most frequently bought together products.

And also we have noticed in the example you are able to add products which are out of stock so looks like we need to check if the product is available then show it as an option.  

If the above can't be achieve could you please share alternative solutions?