Tom,
Most auto body paint supply stores have access to these aftermarket companies. Some salvage yards have gone to that market as well due to the lack of salvage part sales. If not there try Keystone.com. They fit like $25.00 fenders but cost $65.00 but your right they won't be on there long. Owning a body shop is great when your trying to decide if you should take somebody's apex away.
Brad