No idea how to reach the domaion registrar, and I would not find out for you as it is not my business and I really don't have the time for that.
But if you use a good ID checking software to verify the IP, it usually would indicate the domain registrar as well.
For eu domains, you first need to find out where the server is located. Then, google for something like "eu domain registration in X" where X=name of the country where the domain is hosted.
Hope that helps.