Where to find a new replacement radiator for a 1973 Duster?

I'm working on my 1973 Duster 225 /6 car. The radiator looked pretty good from the outside, no obvious corrosion or anything, but I had it at the local radiator shop getting cleaned out and checked, and they said that the more they got into it, the worse it was. Surprised but disappointed.

I took a quick look online and saw nothing but a bunch of aluminum / plastic tank single row crossflow radiators.

Anyone know where to find a copper / brass downflow unit, at least somewhat similar to the OE radiator? Mine was a 22 inch wide 2 row, because it is an A/C car.