The British - Microsoft keyboard layout on MacOS has no icon/flag associated with it, so when using this layout with my Windows keyboard I either have to display the full text of the input name, or have an empty space where the icon should be.
Here's a screen shot showing an icon in the space:
I'd like to fix it with my own icon (probably a Windows logo over a Union Jack). How can I do this?
Related but not the same as What is the location of flag icons for Input method on Mac OS X? which covers the location, which may or may not be some dat files. I borrowed the image above from that question.