That's weird because I find a ton of stuff at REI's Garage Sales and on eBay. A little elbow grease, a light dusting of hydrophobic spray, maybe a little patching here and there... and my stuff works great!
My wife & I have somewhat variable success with this method. You can find killer deals if you are an unusual size. But if you're a Medium in men's or a size 6 in women's, good luck finding anything. Perhaps a little counter-intuitively, the most common sizes are picked clean first.
Also try Patagonia's Worn Wear site!