there is no offical release between these version.
see: Volumio Changelog
There are testversions, but these are not recommend to use!
Anyway. i found these testversion for rpi:
2.753/2.754/2.755/2.756/2.764/2.766/2.767/2.768/2.769/2.772/2.773/2.776/2.777/2.778
(you have to complete the URL and find out the release date by increase)