Just had a look, i see 8:25am LGA to CLE on sunday morning, but dont see any return flights late Sunday night. There is a 7:50am CLE to LGA on monday morning but that lands at 9:30am which is to late for me.
I actually have a reservation for the 5:30pm Sunday night flight. Was holding it until closer to the trip just in case I wouldn't be able to get to work late on Monday morning. Looking like I will be on the 7:50am flight on Monday morning so I can cancel the Sunday night flight.
Not sure if the seat will show as available once I cancel it but it is worth a try. Let me know if you want to try for it so we can coordinate.