What are my options for a fire rated door for a 32" x 36" rough opening?
You could add 5/8" (16 mm) sheetrock to the back of the door.  That would make it a fire rated surface.  If that matched up with the sheetrock at the right, it would be almost a continuous surface.  If I had to live with it, that is what I would do.

If it is to sell the house, the new owners either won't be used to the access or won't know about it.  Sheetrocking it in would be cheap and easy.