Octalink is an old interface that is somewhat rare these days. I don't know anyone that ever made a torque sensor for them. There are a few ISIS sensors out there, but all I have seen are single sided (measuring left leg torque only), except for a few that use larger diameter BB shells, like T47. This is due to the extra space need for 2 sided sensing and the ISIS spindle being larger diameter.
I never got far with my own sensor. In general, you have to be producing 500+ units for prices to be reasonable.