TTL enabled Optical Converter advice needed

I'm planing to upgrade my camera to Sony A7III. The only thing that got me considering is the Optical Converter.
Currently Sea & Sea is the only one that offers one that works on TTL but it's housing much more expensive comparing to Nauticam.
Comparing both housing I need to fork out $700++ for the Sea & Sea housing.
The converter would cost around $500 for either brand based on other models.

I'm doubtful about the Optical Converter performance. Accurate..???
It's too new for the A7III converter. Any model of Camera or Optical Converter that works with TTL welcomed

By the way is there a 3rd party brand that works with the Nauticam Housing?