I know that babies aren't supposed to wear thick jackets in the carseat because it makes it less safe...is something like this bunting safe for him to wear while in his carseat? I can't find the exact one we have, but it's similar to this, except it has feet and is maybe a bit thicker (but still fleece-y).

http://www.gap.com/browse/product.do?cid=8788&vid=1&pid=301459002