As there are many choices available, much comes down to what you like as well as feel best suits your car. Perhaps you can find something similar that was available in the 60's in Portugal (or Spain)?
Below is a still from the 1965 British film The Collector showing a wing mirror fitted to an early Morris Cooper.
![Image](https://www.imcdb.org/i707683.jpg)
Those type of old photos are great to see what really was used 'back in the day'.
Good luck in your research.
![Smile :)](./images/smilies/icon_e_smile.gif)