For anyone else on this thread who is interested, I found https://github.com/mat/besticon which grabs high quality icons from a given URL and it is superb. I've just spent the last hour or 2 filling in a fair few of my missing icons and updating icons which were still rocking low res favicons which just look...π¬
I fully recommend this for anyone else who has slight OCD with icons on any of their 1password entries (or who wants to generate icons for any other purpose). The GitHub project linked above has a site where you can just pop in the URL you want an icon for and get the result without any technical faff...
https://besticon-demo.herokuapp.com
Also, I'm running a pre-release version of 1password and noticed that some of the sites I listed earlier in this thread now seem to be either picking up missing icons and also displaying (matching) icons on items which were either mismatched, or the icon in list view was missing even though there was an icon on the item itself. So progress there it seems ππΌπ. Still, the above site is well worth a look imo.