We are trying to find a Day and Night Air Conditioner Cover Model # 593CJO3O-B?

Better to not cover the entire unit. This promotes rust. Better to just cover the top of the unit to keep leaves out etc. A cheap way of doing this on most units is to use a plastic garbage can lid and ad a weight/rock/brick to hold it down for the winter winds. This is what I recommended to all my customers years ago.