I got mine from Divervision for $699....self installation for a Sea & Sea MDX D300. It think they also have a version for the Ikes which can be self installed...
I love it. The stock viewfinder was terrible. Below is my short writeup on a different forum,
There have been some who asked about the Inon 45 degree viewfinder from Taiwan's Divervision. Thought some may like to know that I bought this (and everything else) from them and installed it myself. I am pleased to report that it was "fairly" painless and I am very very happy with the viewfinder.
Here are some photos;
The reason why I say "fairly" painless is because the stock viewfinder assembly was on real tight and hard to remove without a wrench like this one;
After removing the stock viewfinder from the inside, there was a screw much like the one in the picture above with the two slots that had to be removed. I managed to get it off with two small allen keys slotted into the grooves and twisting in opposite directions. After this, the whole viewfinder assembly could be removed from the acrylic backing.
The Inon viewfinder has two O rings whereas the stock viewfinder uses only one. Mine came with spare O rings. I greased the rings, slotted the viewfinder into place and threaded a locking screw which came with the viewfinder on the other side. Done! The viewfinder rotates easily in both directions and "clicks" satisfyingly into place at 90 degree turns. It is a modified Anthis Nexus assembly and probably a custom locking ring (which has grooves around it to make it easy to hand tighten).
I must say that having this viewfinder has made a world of difference. The stock viewfinder was terrible (I am new to DSLR use UW). It feels so much more natural now and I don't find myself struggling to compose or determine sharpness.
Divervision has been great. They ship EMS so it is fairly cheap. Their prices are fantastic and they replied ALL of my concerns and questions I sent them constantly (within 24 hrs). They really bent over backwards for me (shipping details, seperate shipments, different addresses, etc). My only relation with them is as a very satisfied customer.
Edit: I looked....sorry, no Ike versions at divervision. I do recommend this viewfinder though