...another reference for the 'Son of the Sun' may be found in Philo (in relation to the Logos) - though there more as the Sun of the sun, or the Sun beyond the sun.
Still, it is also worth bearing in mind that in those more gnostic orientations, the Sun, the Son, and the sun are all very much interconnected, both for their radiant light, but also often with numerological analysis, using either (and especially) Greek or Hebrew gemetria.
With this, there is also relation to Mirthras and Hermes... brings back to mind a book I would also highly recommend: David Fideler's
Jesus Christ Sun of God (Quest books, 1993, isbn 0835606961)...
... by the way, the link to
1stBooks.com within the linked site returns a 404 message...