Try Salem Tractor Parts, in Salem South Dakota, we had to get one for our 2166, also picked up parts for our John Deere combines there, the rock trap came off of a 2166 that was burned, we had field tracker and they still got the right part.
Rocktraps are the same for 1600 and 2100 series but if your 2166 does not have a rocktrap you likely have a 60" feeder and you will need to get a 54" feeder as well as the rocktrap.