Go into "Developer Settings" (click on "Build Number" in the "About Device" section 7 or 8 times until you get a message saying something like "Congratulations, you're a developer!"; "Developer Options" will now show up as the last option in the main settings menu). All the way at the bottom, you'll see an option for "Force allow apps on external". Click that and you can move just about any app to your external SD card. Find the app in the "Applications" menu and go into the "Storage" section. You should see the option to change the storage location.
Be careful with that though. Apps that are stored on your external SD card may not behave the same way. That's usually why manufacturers take that option away. If an app starts misbehaving, move it back to internal storage.