Additional or custom icons for dynamic keyboard

In the channel I'm developing, I'm using a DynamicKeyboard with a custom Key Definition file that I copied from the "Full Keyboard with Extended Action Section" here: Key Definition File | Roku Developer

To improve the appearance and to avoid the need to do localization for different languages, I would like to replace the text for "Close", "Clear" and "Continue" buttons with icons, the same way as, for example, the developers of the Disney+ app have done on their login screen keyboard.

I was able to copy the trash can icon for the clear button from the other key definition files but I can't figure out how to make the hide keyboard and right arrow icons appear for the other two buttons. Is there a list somewhere of all the possible "theme:DKB_...KeyBitmap" values that can be used for icons? If not, is there a way to use our own custom fonts or images for icons? Ideally, I would like to have a magnifying glass icon symbolizing search on the continue button.