I had a key switch lamp on a '68 Barracuda. I would think the most difficult to find part is the key surround - which I assume you have.
It was an option only with the light package.
http://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1969/69_Dart0021.jpg
http://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1969/69_Dart0022.jpg
I think if you are patient you can find both used since probably the same parts were used for several years and models.
If you haven't yet, get a '69 parts book. With the factory part number, often you can figure out what else it was used for. Some still show in the Chrysler system. You never know until you try 'em.
