Do you mean a mid entrance door or the drivers door? The mid entrance door on your model looks very much like mine on a '94 Fleetwood.
I'd be calling with the doors measurements and Brand/Model info to salvage yards
...there must be hundreds of salvage yards all over the US. Maybe you'll run into some yard that has a cross reference and you would be able to use a Fleetwoods door on your Winnie. But I don't know if they are the same size and all, they just look very similar.