The blue blazer can come from any department store; the oxford has to be 100% cotton, and pressed; ideally the jeans would be Wrangler, because that's what real Colorado cowboys wear; and the cowboy boots have to be pointy, and can't be one of those new fangled pairs with laces.
It can be accessorized with a wide brown leather belt, hopefully with leather stitching along the edges, and with a big shiny rodeo belt buckle. A cowboy hat of any kind is also a good accessory.
"Yeah, his Border Collie wouldn't stop barking last night. I think it's name is Denali."
"Of course, his car has Colorado plates."