Like you, I was looking for a Midi controller to add more expression to my playing. I thought that the BC-3 might be the ticket but found it a little non-linear in its output. In addition, moving air through the device was more distracting than I had hoped (not to mention dizzying!).
As I was using the device, it occurred to me that if I had a controller that responded to bite pressure, I might have something more usable. Several of the commercial wind controllers offer something to this effect. But I found no commercial devices that offer this type of midi controller individually.
After a little research, I found a company which caters to robot experimenters. They sell force sensing resistors. I fabricated a device that consisted of one of the FSRs hotglued between two small pieces of hard plastic. I use potentiometers to adjust sensitivity and range. It plugs into a Midi Solutions expression box (you can also use a Breath controller box).
This has worked very well for me. After a little tweaking, I’ve been able to achieve very smooth and accurate midi control through the device. When I lightly apply bite pressure, the control change parameter gradually engages and as more pressure is applied moves toward its maximum value. A couple of trim potentiometers can be easily tweaked for best effect.
I still receive some benefit from the Yamaha BC3; I used the boom to mount my bite controller. (One could ,with a little work, mount the bite controller directly on the mouth piece of the BC3. You could then have both breath and bite pressure controlling different CCs)