Worked in the cattle business for a long time on and off, from calving to tanning, I've done it all. I can tell you, just get your leather wholesale. "Straight from the cowboy" tells me "an arm and a leg". A LOT of work goes into processing cowhide to leather. If someone like me goes through that kind of trouble, you'll pay $500 to start, likely closer to $800.
Repurposed leather is likely your best bet, belts coats, even boots. If you want good stiff stuff, like saddlery, you'll want steerhide. Its what high quality holsters and saddles are made from. Finding that stuff will be hard, at least repurposed, you'll have to buy it.