I am using a set of FSA aero brake levers and they are by far the best levers I have used. they were a little noisy at first but the lbs put some liquid grease in it and its like butter now. I don’t think it has a return spring though but it meets all your other requirements… may be worth checking out.
The levers that fit all your criteria are Profile Quick Stop 2’s. Aluminum, internal, return spring. Get 'em.
I second Greg’s recommendation, I have the Profile levers mounted on a Syntace base bar and they have a quite nice feel about them. I didn’t think the return spring would make that noticable a difference but they do…and they’re not as expensive as the carbon Cane Creeks or Blackwell’s.
Miguel in the 'No…El Tribato