The copay for Hawai'i is waived for elite members on flights to/from LAX, SFO, DEN, and ORD. If you're flying direct from EWR, IAD, or IAH, see if you can SDC to an itinerary with a connection at one of the other hubs to HNL. Then you can upgrade (if still available) w/o copay.

If you want lie-flat, you need to shoot for the 767-4 (UA 73) afternoon flight out of SFO. Looks like the F cabin is already full for tomorrow's flight, though. You might have some luck on the 777s.