Does the Inon 45 degree viewfinder have a diopter adjustment? Looking at several sites I have not found the answer.
No, it doesn't. And I didn't need it anyway. My camera had the dioptre adjusted on land when I first bought it, and I haven't touched it since, and it has been in the Ikelite housing with and without the Inon viewfinder. I personally do not see the benefit in a dioptre adjustment on a viewfinder, unless it is a rental housing.