Is there anywhere one can buy or find plans to build a human powered aircraft?
Yes, contact Todd Reichert, PhD, or Cameron Robertson at Aerovelo Inc.   They have designed, built, and demonstrated the first human powered vertical aircraft at the University of Toronto, of which they are alumni, and they won the Sikorsky prize of $250,000 for it.

They have aero-velomobiles that can smoke the albatross.

Note: The ability to get airborne in these Ultralights is heavily dependent on the weight and athletic ability of the human operator.