Never overlook your local resale shops after you know what you want or need.
What happens many times is someone will get a shirt or vest that looks to "costumey" or otherwise doesn't fit in their wardrobe, then they donate it to local charity & it ends up in a resale shop.
I recently found a shirt made of combed silk (looks & feels like cotton) with a banded color in a natural (near white) color for $1.00!!!
This shirt looks about as period as any $40 Wah Maker offering & I got it for a buck!
I've also found victorian styled vest with lapels & never more than $5.00.
It's worth checking out, and remember, any money you save on clothing can go toward better guns
eBay is also a good place to check, do a search for "SASS cowboy" and check what's there, they also have an entire section dedicated to Men's western clothing, sometimes you can find period clothing for a song.
Take Care,
DB