I organise a few copywriters on
Copywriters | Top quality content
While we haven't done FB campaigns, I don't think there would be any reason as to why we couldn't help you out. If you are thinking of outsourcing this, you should think of clear guidelines as to what you want the poster to do. i.e. level of interaction, creation of content, posting of content, etc.
Outsourcing sounds easy, but it will still require you to do some work