I got a sweatshirt, sweater and vest from Wal-Mart a couple days ago. I took Couver in and tried them on before I bought them though, because I always misjudge his size and buy too big or too small.
You also have to make sure they have a hole cut for the harness to go through during walks. This is something I did not look for when first buying clothes for Couver and they cannot be worn on walks