The longer a season has passed, the more likely you will be able to find it. However, if you are wanting the seasons of one show to be all on one location on the internet, it is very unlikely. However, Amazon prime and some of these other big-name places are your best bet. The first three seasons can be purchased on Amazon on DVD, but the rest when searched shows a variety of the winners and their CDs.
However, the show itself doesn’t look like you can get it on Amazon Prime unless you want to piece it together. There are a few excerpts from the seasons especially the finales. To find the entire seasons and shows, I would not look on Amazon Prime.