I woul post a wanted ad on craigslist. In the medford-ashland section there's been an old Simco saddle for awhile, for cheap.
Also - Don't forget about the turn. You said she's fast, but you can have the fastest horse in the world but if you're blowing out twenty feet every turn someone can walk the pattern faster than you. How do I know that? I once thought I had a gaming horse until I got there, blew out EVERY barrel, and the peewees got better times....Embarrassing o.o
If you just want to play though, I would suggest TDSC (If you don't know its Trail Dust Saddle Club) SOBRA and Posse are more competitive, TDSC is really low-key and everyone is very friendly.