Modify keyboard flag icon in menubar with ResEdit?

I'm running System 7.5.5 with a menubar keyboard icon that shows the national flag of the current keyboard.

I've used ResEdit to import into this system a keyboard layout from a System file on another machine (it's in the KCHR resource), but I can't figure out how to assign a flag icon to the new keyboard - or copy an existing flag icon to the new keyboard definition. I've searched through quite a few resources, and can't find the flag icons, and can't find how to link a flag icon to a keyboard layout.

If anyone knows how to do this, I'd be very grateful for details of exactly which resource to use. Thanks.