Yes, but I don't think it will return the results you want. When you enter search criteria into a portal while in find mode, you are telling filemaker "Find all records in table 1 that have at least one related portal record that matches this criteria." You can select New Request to enter a second criterion in the portal, but then you are saying Find all records in field one with related portal records matching Criteria 1 OR Criteria 2---so this still doesn't produce what you want.
Perhaps a different approach will work:
Switch to a layout based on your portal records. Perform your find on this layout and sort by your key field to group the records by product in descending order. You can omit records off the bottom of the list to remove records that are too infrequent to be of interest. You can now use Go To Related Records, Match all records in current found set in a script, to locate the product records on your original table/layout.
Note: Go To Related Records is complex, with many undocumented features/issues. See this thread for a complete run down on this powerful tool: