We have Software Assurance (SA) licensing and therefore should have access to the SA Edition of Software Update Services (SUS). I cannot locate the appropriate CD nor can I find any information on Microsoft's web site which would indicate where I can obtain this software.

I have contacted our Microsoft representative without any success in locating this software. Can anyone assist me in obtaining this software whether through downloading or the appropriate CD? Does this version actually exist or is Microsoft's web site inaccurate?

From the microsoft.public.softwareupdatesvcs newsgroup
The SA version is still in beta and isn't available yet. Rumour has it that it might be available as early as March but remember it’s only a rumour.