I've always been able to get the hoses for My Mk 8s through Auto Zone stores, although I've had to wait a day or so, untill the next truck from the warehouse had been around.
On one occasion, I didn't want to wait, so I took the old hose to a Napa store to see if they could match up the bends in it with some other hose they had in stock. They had one hose I could use by cutting it shorter at a certain point, and the cut-off section even worked as a replacement for one of the shorter hoses which I also needed.
The hoses for the Mark eights are sure to become more scarce, now that our cars are at least eleven or twelve model years old, now. So if you do find the part numbers are finally discontinued, you should be able to come up with something by using the same method as above.
Lead Foot
Crazy 'bout my ol' Mark 8s