I just added a feature to Replies and more for Google+
that adds a dropdown next to the share menu with additional sharing options.
I'll eventually make these pluggable and easy to update so that you can share posts elsewhere. Note that sharing a non-public post may not appear pretty on Facebook.
As usual, you can disable this from the settings page.
Grab 1.14 here: https://chrome.google.com/webstore/detail/fgmhgfecnmeljhchgcjlfldjiepcfpea