Not sure what model # you have but try these two sites, both Carry KitchenAid parts. culinaryparts.com or partstore.com. I have had good luck with both companies, even for equipment that is outdated. It will help if you have your manual with a blow-up view of the parts with numbers. Some times they use odd part numbers.
I don't know how mechanical you are, but I had what was about to become a similar problem with my KitchenAid. I took it apart, found a seal that was shot, reseated it, packed a bit of grease in and it's still working today(although, I gave it to a friend who mostly makes cookies). I bought a Delonghi 7 qt and have been very happy with it, although if all you're going to do is mix is dough you have other options.