I found exactly the same problems when I tried at first. I even went as far as going to the countries and city forum and asking there for contact details. Felt like a stalker lol
I have to say that once I got my first appointment it seems to open doors a lot faster when you mention who you have work by, even to the extent of moving you to the front of the 1 year long queue. Shouldn't really be like that but it seems the more talent and name dropping you have on your body, the faster they want to be a part of it....
Another thing that appeals to the high end well known artist's in my experience, is giving them total freedom to do what they like will see you get a response and seen quicker.
I will be honest and say that most of my first contact emails to them starts with, "Budget is not an issue and you have total freedom to do what you like if my idea doesn't appeal. It seems to work lol
Obviously when you get a reply then move forward with some ideas.
This is only in my experience and what the artist's have said I could be wrong but it worked for me :-)