I believe these are what you are describing:
Just an FYI, the 416 receiver rail is 3/8" higher than a standard picatinny rail, so these will be much lower than you are accustomed to looking through. Just though you should know.
Steven_Deschain just sold a set to Cohiba recently in the EE, but it was the flip-up front sight that attached to the proprietary HK gas block. He may be able to get some more.
Also Jerry H over at HKPRO had some for sale recently.