Options:
1) You can order service pack CDs from Microsoft. Check out the following
knowledge base article
http://support.microsoft.com/KB/326246 and look at
the fifth bullet point down under the MORE INFORMATION heading.
or
2) If you don't want to pay for the CD, you can also download the self
extracting executable* for Visio 2003 SP2 on a machine with a more
tollerable Internet connection, then copy to removable media and copy onto
the machine with the slow 56K connection.
*You can find the self extracting exacutable for Visio 2003 SP2 by going to
http://download.microsoft.com/, typing in the words 'Visio 2003 SP2' into
the search with All Downloads selected in the drop down, and click Go. Then
click Visio 2003 Service Pack 2 (SP2), then click on the Download button and
the Save button.
or
3) Get a faster Internet connection. Just kidding
But seriously!
Hope that helps!