Yul Brynner's Magnificent Seven / Westworld 'Gunslinger' shirt

[Edward]

I'm interesting in finding a shirt the same as this one, worn by Yul Brynner in two of his iconic roles - his turn in The Magnificent Seven, and his appearance as 'the Gunslinger' in Westworld, which echoed the same character. This is the actual shirt:

Any leads? It's not especially Western, just a basic, workshirt design that was around for decades, but I can't find a matching one anywhere new. Appreciate any links folks have!