It was he, together with Terence Donovan and David Bailey, who fearlessly pushed aside the conservatism of the 1950s, rejecting studio portraiture for innovative and dynamic fashion shots. Nicknamed the Terrible Trio by the newspapers, and the Black Trinity by Norman Parkinson, these men were on a mission to break down existing photographic conventions and create a revolution in British photography.
Known only by their surnames, the trio became more famous than the people they photographed, and though competitively creative at work, outside the studio they became fierce friends with an enduring loyalty to each other. Duffy, who was always considered to be the most intellectual photographer, worked relentlessly for more than 20 years, and covered every genre.

Comments: 0
I like vintagevixen.com (click on Wild 60s and 70s wear). You can try vivalavintage.com but they're a little overpriced.
Basically what you want to look for is:
Anything polyester.
Bell bottoms.
Bright and colorful loud prints for early 70s, earth tones for late 70s.
The stuff you will find vintage