I went through the same process a vew months ago, From what I understand, the Nikon duel element diopters are the preferred ones, but are not being made anymore. The 5T and 6T are 62mm, but are very hard to find. Occasionally pop up on ebay, but selling for alot. I found a 4T on Amazon for about $30. The 3T and 4T hae 52mm threads, but still works fine when used with a step down ring.
attached is a chart with good info for some diopters including the Nikons and a sample pic I tok with the 105VR and the Nikon 4T.
As a word of caution, especially for a new guy like me, shooting like this is a lot of work. My DoF is very small and shooting in Monterey with some swell in a bulky drysuit takes a lot of patience. I love the results though. A very powerful focus light helps alot.
Take care,
John

