Hi authentic is not a good word to use. Most of the places where you will have access to Original New brand Phones will use the word authentic to describe 1:1 copy. I can show you a supplier in HK who can supply Original New brand Phones product for you. However only the Apple have a worldwide warranty.
The margin on these Phones is not great . Word is Vodafone get about 5% on iphone. Mostly it is all tied up with the networks as the original source and as small supplier it is hard to match the promos being offered currently as telecom tries to convert their CDMA customers. But I have a few sources