You build a portal on a Customer layout that shows related Product records.

You write a script that uses a Go To Related Records [ ] script step to navigate from a Customer layout to the desired set of Product records.

You create a button on a special Customer layout that performs a Copy All Records/Requests[ ] script step and allows users to paste the result into a Find request.

You loop through the found set of Customer records, assembling a set of ID values into a global variable. You then loop again on a Products layout, creating single find requests for each ID value.