Look my hunt for the worlds fittest woman has taken me accross every continent in the world (apart from Aus so far) and 42 years and..... Oh sorry I see what you mean.
Or you could contact Community action treks Nepal. run by Doug Scott that splendid chap. As a matter of fact responsibly organised trekking is probably the sustainable and most environmentally sound way to go. And after all you go there because its nice dont you? So keep it nice! dont use local wood for fuel try and bury any human waste etc.
SOme of my colleagues do NOT agree with you having been stuck in one for a couple of hours with me! ( I know it whiffs a bit but I was trying to warm it up!)