Part number 320-1275 is in Sun's Sun Ray 1 Spare Parts list. However, it's not on the store.sun.com web site.
It didn't work the first time I turned it on; I had to install some modules by hand (they didn't get modprobed correctly). Here's the list of currently installed modules on my working system:
pirx: lsmod Module Size Used by sr_mod 13112 0 (autoclean) af_packet 7868 0 (autoclean) hid 10724 0 (unused) keybdev 1612 0 (unused) usb-uhci 20648 0 (unused) usbcore 45600 0 [hid usb-uhci] input 1948 1 [hid keybdev] tulip 33024 1 ad1816 8828 1 sound 57708 0 [ad1816] soundcore 3492 5 [sound] isa-pnp 27528 0 [ad1816]At least some of those are doubtless not needed. I'd guess the necessary ones include hid, keyboard, usb-uhci, usbcore, and input.
I started to create an xkb setup for the type 6, but got interrupted before I finished it. My partial work is xkb.diff. You'll likely have to be an X hacker for this to be of any use to you.
The requisite hackery for /etc/X11/XF86Config:
Section "Keyboard"
Protocol "Standard"
XkbModel "sun_type6_usb"
XkbLayout "us(sun_type6_usb)"
XkbSymbols "us(sun_type6_usb)"
EndSection