Window sourcing
My SWAG is that Ericson (and most other builders in that era) sourced their windows locally from a firm that was set up to supply the RV industry. A short-run design like that would not generate potential income to justify keeping patterns and parts available like it would for a production boat with a 5000+ output over 20 or 25 years, for instance.
If the corner radius is too severe for a modern supplier to bend in aluminum and you want to keep the 'signature' shape, best to change to an external acrylic or lexan lens, like the factory fixed ports on my model.
http://www.boatwindows.com/products/standard-duty-fixed-window-series-1150/
I have seen this company's custom windows on a Cascade 36, with smoked glass. Quite good looking. Stunning, actually.
The unknown is the current cost. Best just to make a pattern and have them quote you. As their site information points out, you might also have to modify your radius.
Regards,
Loren