Bookable through
Priceline or, to search for dates and book, use
Google FlightsORD-MIA Example Dates:4th-12th Apr
4th-18th Apr
5th-12th Apr
5th-18th Apr
5th-19th Apr
11th-18th Apr
11th-19th Apr
MIA-ORD Example Dates:12th-18th Apr
12th-19th Apr
This can work well for the entire Pesach or just second days from ORD, but may be useless from MIA. More dates may be available.
HT:
SF