No useful partner -- you'll have to just buy the LIS - OPO flight and leave enough buffer time to re-check (or start your trip in LIS and then go up to OPO a couple days later).
As noted your other alternative is a connection via CDG/AMS -- both AF and KLM fly direct to OPO (although not sure if daily/seasonal/etc) so that would seem to be a good option unless JFK - LIS + LIS - OPO TAP add-on is significantly cheaper