I recently had an email from a psychology student in Sweden asking about the published 'gurus' in the field of Authentic Leadership research and any questionnaires which currently exist to measure AL.
Bruce Avolio is one of the most well published academic authors on the subject, whilst Bill George is probably the most well known practitioner with his book, True North.
Goffee & Jones with their book and Harvard Business Review article both entitled, "Why should anyone be Led by You?" straddle both theory and practice. They have a very easy writing style and are well worth a read.
As far as I am aware there isn't a commercially available 360 instrument that measures AL, certainly not within the UK anyway. This of course is one of the reasons that I am currently developing one myself within my PhD!
Walumbwa and colleagues (which includes Avolio) have developed a 360 in the US which they very generously make available for research purposes to bona-fide students, however I'm not aware of it being accompanied by a business-focused feedback report or any specific development activities.
I will post more about my own PhD research into AL in due course!