Up for sale is a Nauticam flip diopter holder made for the 4" port, 36137, for the 9-18mm wide zoom, but can be used with the 12-50mm if your camera can operate the electronic zoom feature, and the 60 macro (without flat port optical quality). I used this with all three lenses, and the flip diopter allowed use of a M67 macro diopter for close-up photography. This is in fine, working condition, and sells for $362 new. $175 here, including PayPal fees, shipping and insurance to the USA. If you're from outside the USA, you will be responsible for shipping costs, VAT and your country's import fees.