We searched high and low for a ball that Soffie and Griffyn could not tear up! Griffyn lives to herd a ball. We came upon this company that makes the boomer ball----they even make balls and toys for lions and tigers! They do make a ball for dog herding, but we thought it might be too big for the corgi. So we purchased the smaller cheaper ball. It is made of a hard plastic so it is an outdoor item, but you can fill it with sand or water for a different experience. It isn't a ball for playing catch---just for pushing along the ground. Griffyn loves it---he chases it around the yard and I can't see this ball being destroyed. Here is the website for the ball and other items and a few photos too.
http://www.boomerball.com/