80x30 interior door (w/ cat flap?) (Baltimore City)

Looking for an interior door to cut a cat flap into so I can replace + store a door in the townhouse I am renting and put my cat's litter box in that room without the dog getting into it. The current door measures 80" x 30". I am not picky about color or style so long as a cat door can be installed if it does not already have one. I am able to pick up during the day and evening most days; willing to drive.