There are TONS of tack trader groups on Facebook. Under $1000 you can likely find Billy Cook, Circle Y or possibly an older Crates. Can occasionally find a Bob's or M.L. Leddy for $1500+, but I love my Continental Reining saddle and would personally start at their Specials & Bargains page
Continental Saddlery Inc. And
www.horsesaddleshop.com usually has a good selection of brands in all price ranges.
Have you ridden in any brands that you loved or disliked? Any brands that tend to fit your horse better than others?