N8 is not the caliber it's the date code (N for the decade, 1970's, and 8 for the year number, so 1978).
Are there any marks in the main plate underneath the balance wheel?
This is a french made movement so I suspect it's an FE, possibly a 140-C
I can only find these. Do you have the means and skill to make them? Have you tried ebay? You should be able to find what you want in a selection. Here is the link to what I found.