Require masked or irregular shaped widget visibility/cursor interaction

I have a world map in a widget assembled like a jigsaw puzzle using a number of masked materials as images. I have code set up and working to highlight an image while it’s being hovered over, but the visibility/cursor interaction seems fixed to the rect of the image, even with a masked material.

In the screenshot you can see the image rects for Asia and Russia. The Asia box in this case has taken priority and Russia will only trigger ‘isHovered’ once the cursor leaves the bounds of that green rect. I’m looking for a solution to more accurately represent an irregular shape such as the border between countries. Rough approximation would be fine but masked via texture would be wonderful.

https://forums.unrealengine.com/community/community-content-tools-and-tutorials/96724-free-custom-shaped-buttons-custom-hit-box-for-any-button