But it is rare on the used market and highly priced when offered... Guess what?... I missed one 2 years ago here in Paris at a well-known seller specialized in medium format. It was in mint- condition and at 1,400 Euros!!!... Yep, 1,400 Euros!! I wanted to think about it and it was gone the day after I saw it (and touched it...) 
If longer and better is what you are after your best choice is a Super Achromat.
C and CF give about the same results.
With a 203 FE body the CF is the best choice.
A good Super Acromat is will demand more than 2000 USD.