The best ones are probably too busy writing copy for their own stuff.
I used to write copy for others in the past. I still do for a few friends. But really, if someone can create copy that converts, eventually they're going to realize that writing for other people is a waste of time unless the pay is just rediculously sick.
If you have any specific questions you can post here or PM me and I'll be happy to offer some advice if it helps some people out.