Moderately priced used, look for any of the modern plasmats, like the 135mm or 150mm Schneider Symmar in various versions, Rodenstock Sironar-N, or their less expensive Caltar branded versions, Caltar II-S (Schneider) and Caltar II-N (Rodenstock). The Schneider 150/4.5 Xenar is also a nice compact, inexpensive lens, good for portraits, but it doesn't have as large an image circle as the plasmats and won't be quite as sharp in the corners.