There is no such thing as a portrait lens for 35mm the 85 -90mm thing is nice to get a distortion free image but in reality take the focal length you are most comfortable with if you feel comfortable the model will feel more comfortable too. A 50mm can be used for portraits quiet well so can a 35mm and 20mm (for example some nudes by Jean Loup Sieff 21mm Super Angulon, Bill Brandt etc..) the distance between the photographer and the subject is just as important as the focal length imo. BTW 135mm is a Portrait focal lenght so is a 180mm lens.
I recently discovered the 75mm focal length and absolutely love it in fact I vastly prefer it to the traditional 90 to 105mm portraits focal length. The 105mm p-Auto Nikkor is my favourite landscape lens for 35mm.