Commercial Ektars are good performers and are often on EBAY.
They produce sharp negs with good contrast. You will proably need to have the Ilex shutter CLA, but the one I bought a couple years ago had a very good shutter that needed no work at the time.
Another option is the older Schneider Convertible lenses such as the 300/500. it is heavy and comes in a Copal #3 but usually sells for under $500.