I've given the product number from Riley in my earlier post, I don't think you'll be able to order the fitting direct, and website is not much good for gaining specific information. The catalogue I am refering to is the latest.
Peter is right though, if you want a more modern, fixed fitting the AHPC gooseneck would be the way to go, you would looking at $75.00 for a AHPC gooseneck, I don't know what your replacement Riley fitting would be.

Regards