You can order a 24x60 prehung 6-panel door at HOME DEPOT.
Also depends on budget, skills, and look you are going for. A flush hollow core door is inexpensive and can be made any size, but the cut end needs to be re-blocked for stability. A solid wood door can be cut anywhere, a raised panel door limits your options because you can't leave half of a panel. Also, consider knob and hinge placement after the door is cut.
If you can live with 24" wide I would consider the prehung from the Depot.