bluetooth - How to add a physical keyboard layout

I'm using a Logitech Tablet Keyboard for Android with Galaxy Nexus (Android 4.1).

When I go to Settings -> Language & input -> Physical Keyboard and tap on Logitech Tablet Keyboard Gen there is an option to "Set up keyboard layouts". There are many predefined layouts but the "Polish (programmer)" keyboard layout is missing. How can I add one?

I have looked at /system/usr/keylayout and /system/usr/keychars but I don't see the other layouts there.

I know there is an app that does not require root, but it's aa virtual keyboard that works with bluetooth keyboards https://play.google.com/store/apps/details?id=com.apedroid.hwkeyboardhelper and I'm interested only in adding the layout to the built-in physical keyboard layouts.