Beard, they dont make them anymore. In fact, they never did for the c5, it was a previous gen accessory.
I've seen one and its just a piece of rubber pipe with a screw collar and a plumbing section from the hardware store (4"through piece with a smaller side outlet), then they use a filter and cap just like mine from a auto parts store.. its probably $25 in parts. They also spray paint it black and made some mounts from pieces of metal.