do companies offer this type of housing? why not?

[yaronad]

Yes I add vacuum leak sensor

The ergonomics is simply fantastic!
one hand 3 fingers! to control all functions and set A / S / ISO and focus / trigger
it is very very effective underwater - you can see it for your self from the housing pics and videos at thier site

 

[johnkendall]

I've been using an Easydive Leo 3 housing for about 3 years. It is awesome. Very very easy to use as the buttons you need are right under your thumbs. It actually works well below 100m deep (I've had mine down to 135m)
Most bodies have already been measured, so you can just ask them if they have a base available for the camera you want.
Only downside is that the housing is quite large, but this has a good side effect of making it slightly positively buoyant, so you can weight it how you like.

Thanks
John