The dpr post explains a lot, since the repairman who gave me the part number probably used the same Nikon source, which appears to be wrong. So, it seems, Ali Baba probably sent the part number I asked for. If that is the case, perhaps they have the right one. I don't remember just how I found the link originally, but I do remember that by searching long enough for the part number, I found a link that led to China, and the part was inexpensive and did come.
As I said, the repairman I dealt with did manage to get the elements apart, cleaned, and re-glued with what he hoped was the correct adhesive - something more modern than balsam - and the result was disappointing, apparently with enough difference in refractive index that, though it looked not too bad at a distance, it was unacceptably soft when looked at up close. Reinforcing my reason for taking gear to him over many years, he ate the repair cost, which included initial disassembly to diagnose, and another disassembly and reassembly for the repair.
I do hope that it's possible to acquire the correct part if the number itself can be accurately found. Or, perhaps, to consult the fellow in Taiwan. I'm giving mine a rest, since I have a couple of other options that work well enough on the D7100, but keep it as a body cap on another old Nikon, hoping that something will turn up unexpectedly.
