You can start from either end (laptop or User A) and find the other.
Let's assume you have a buyer-centric index like the doc I used for figuring out which first names are strongly related but instead of person names you have an array of SKUs (product codes) that each user has purchased. I see you also have product types and categories - these could also be stored in each user's purchase history.
Using these documents you can then draw out the strong connections e.g. people who buy ipods have a tendency to buy Beats headphones. This is the same principle as people who call themselves Robert also tend to call themselves Bob.