I've been checking recently with both Norcold and Dometic.  There is no
3-way current model that comes even close to fitting the cabinet opening.
Even the 12V only model another member mentioned is about 6" short, and so
wastes a lot of the space.

I have come to the conclusion that it is best to become our own expert on
how to make your old Dometic perform at its best with good maintenance and a
few enhancements mentioned in the archieves of this list.

Paul