Grease/tamper monkey script to look for specific HTML in page and alert

I would like a grease/tamper monkey script, that when I visit a page, it looks for the following HTML on the page, and if it is present alert.

<p>
  <script 
    type='text/javascript' 
    src='https://site_im_visiting.com/?a(6 hex characters)=(numbers)'>
  </script>
</p>

Additionally, I would like to look inside an array (of about 4k sites), to see if the site is in the array.