Just came across this thread. I have much the same problem myself. If you model in 1:20.3 scale (Fn3) there are several sources for western figures to be found across the pond. I realise that it can be expensive to get these posted from the USA to the UK which makes populating your layout quite expensive.
I would mention Fine Folk Figures, Supply Line Models, Fun & Games, Just Plain Folk, and Railroad Avenue which I have come across as potential sources. Some of these can be hard to locate on the web, especially in the current pandemic, but let me know if you have any trouble and I will provide details of my researches.
If you are looking for 1:22.5 scale quite a few of the Preiser range would pass muster, especially the US Track Workers models.