How do I crop an awkward shape not just a square/circle etc

Hi I am new to Resolve and have been following a lot of Youtube videos and trying to figure out how to crop a video of an awkward shape.

The video is of an old windows 95 PC loading up and the monitor is slightly curved, so its not quite square.
I want to crop only what is on the Windows 95 monitor so I can then move this boot up sequence to another separate video.

I cant use the square crop because of the slight curve on the monitor in the video it cuts off some of the screen or leaves in the white from the monitor.

I cant figure it out and most videos just tell you how to crop the different shapes square/circle etc.

Thanks in advance I hope I can sort this.

Polygon Mask in Fusion maybe?

on color page use "curve" power window.
right click in node window, add alpha output
connect blue square from the node that has the power window to alpha output

I'll give it a go, thanks