Status Bar Switcher for Speech Synthesis Voices under OSX Yosemite 10.10.3, written in Swift (only testet under OSX Yosemite 10.10.3, it still should work under Sierra) Just download the dmg and use as any other app. I like to manually add it to startup.
source for the flags: http://www.famfamfam.com/lab/icons/flags/