For starters - sign up with WowMedia and promote the WankoffWorld site with at least 6 Latino Cowboy videos/galleries. And it looks to be a recent series of vids so they may be adding more. (and there are some shoots of guys dressed as cowboys that aren't part of the series - so do look through the sets)

Then head over to BlueLoot - their Amateur Jerk Off site has some "cock loving cowboys".

You already have BadCowboys from Real-Bucks

OnTop Productions has http://ontopwrestling.com - with a Cowboy Wrestling Video series. Not sure how you can promote them, you'll have to look around for affiliate info.

Do you have an AEBN account yet? Lots of cowboy videos you can promote, and I do believe you can setup a feed of just those videos if you want to do RSS feeds for a blog. At the very least you can search for cowboy videos and then do posts for them and probably download a clip.

They also represent Raging Stallion/Gunzblazing now and that site had/has cowboys in some of their material.

You might want to include "southern boy" sites also - so look at http://www.southernstrokes.com/

Pimproll has a cowboy site called Barebum Mountain

I have a list of movie titles - perhaps you can track them down in some of the video sites or aebn type sites and promote them that way.

Asphalt Cowboy
Back in the Saddle Again
Big Balls in Cowtown
The Big The Bad and The Ugly
Bookstore Cowboy
The Great Out of Doors
Hang 'Em Cowboy
Hung on the Range
Lust Shack
Meet Me at the Fair
Ride 'Em Cop 1 and 2
Rump Riders
Saddle Tramp
Studs on the Range
Ten Gallon Stallion
Triple X Ranch
Motel Cowboys
Man Scent
Oklahomo!
All The Sexy Cowboys
Below the Rim
Black Cowboys and Studs
Cowboy Fever
Roll In The Hay 1 and 2
Stud Busters

If you have sites that you want to do link trades with let me know -- I have www.saloonstuds.com and still need more trades to it.