Why don't you go for a secondhand saddle? You can get quite good ones from reputable saddleries. We recently bought a nice leather one for our pony for about $400. I'm sure they'd have cheaper ones though.
When I bestride him, I soar, I am a hawk: he trots the air; the earth sings when he touches it; the basest horn of his hoof is more musical than the pipe of Hermes. ~William Shakespeare