I take it you haven't paid for a new flight? If not, don't, not yet. Don't cancel whatever you do, and be wary about paying extra.

This looks like the best bet today with a seat in J on both legs but you'll really have to shift to get onto it.



Otherwise you may need to hold out until tomorrow. This looks like a slam dunk E261 for $600ish per passenger, which may take some of the sting out of it. I can't see any potential routings today, everything except the flights referenced above seem completely full.
See Disruption Assistance thread - signposts and what you need to know - FlyerTalk Forums for more information on what to do.