IMU BNO055 Alternative?
The fate of BNO055 is unknown at the moment. Quite for a long time Bosch was pushing its own alternatives without pre-programmed fusion software, like BMF055. On one hand it allowed developers to make their own changes, on the other you had to pay license fees for BSX software, which I suppose was the whole point.
Now Bosch partnered with CEVA Hillcrest Labs. CEVA programs Bosch parts with their own software and sells them as BNO085. I guess this arrangement is more economically beneficial to Bosch, so BNO055 started to disappear. Unfortunately, CEVA seems to be even hungrier than Bosch, you cannot even download the datasheet without registration with them.
You may try your luck with BNO085, of course. But in the long run you may be better using one of hundreds 6- or 9-DOF sensors and running your own fusion software separately.