I wish we had jerseys like those at our local Goodwill. All you'll find in the sportwear section are old leisure suits and velour bottoms.
All of my jerseys have either come from thrift stores or garage sales. Ditto jackets, and some shorts. I see more bikes than riding gear, but when I do see gear, its cheap. But thrifting is just about a full time job around here. I would try to identify the thrift stores in your area that tend to get bike stuff. And then look in all of the departments. My wife's last jersey was in the kids department.