Congratulations for your search and finding it finally.
For a watch of that age it looks in very good condition from your picture.
The strap color is quite a personal matter but I was thinking for the future looking at light brown tones.
My other choices are light, middle or dark grey but maybe it wouldn't be the best choices for a vintage.
So a kind of brown or caramel, coffe color but maybe you can also play with the material (no croc thus no-scales pattern for instance or mate finish etc...).
Enjoy your new watch, thank you for sharing it with us
and keep us informed when you have your new strap
Best, Mark