Yes they were available with rock traps. Guess a combine bone yard would be the best place to start looking for one. Maybe your friendly CIH dealers or searching on www.google.com would turn up one.
It's listed right in the attachments book Case IH have. You have also to buy some other parts to complete the package. Any CIH dealer worth his salt will be able to put one on. But they are not cheap. I had a rock trap and a feed reverser on my old 1460. My 1660 has a rock trap and feed reverser also.