I hit it lucky years ago. I was able to find a bag of partially quilted pieces at Goodwill. It must have been defective for it's purpose and was in very large chunks. I use them all the time, cut off some and begin sewing to try out new patterns of stitching or even to make sure I have all settings correct on my machine.
This appeared to have been meant for a bedspread by some company since the quilting lines, all just straight lines and very far apart, making it easy to practice on.