https://en.numista.com/vous/index.php
at the end is
» View the country list with my collection quantities.
then you want the middle choice from
Show countries:
from which I have coins - from which I don't have any coins - all
1 - Go to My coins --> scroll down to View the country list with my collection quantities --> from which I don't have any coins
2 - start a Search for whatever country with the Option : My collection:out
If you want all that (in my reply) in a spreadsheet, I did that just now ...
by going to top left of that section, then dragging the cursor down a
few lines (the blue highlighted part), as a test, and right-clicked to copy.
Then lastly, on a blank Excel page, right-clicked and pasted.