Theres this one on ebay just now:
https://www.ebay.co.uk/itm/384751613446?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=5f4y5PCVRv-&sssrc=2349624&ssuid=z-78gemqRYy&var=&widget_ver=artemis&media=COPY
A 22mm variable iris can be bought new here for £55. Genuine as I bought one myself.
https://www.ebay.co.uk/itm/Centra-Iris-Front-Sight-Vario-Swing-/194282328991?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=710-127635-2958-0