I have not tried this with/against the SAP connector, but you should be able to do this with an LCStream object on the SAP side of your code. After you have the Notes document with the attachment your code would look something like this:
Set field = notes_fieldlist.Lookup("my_attachment_field")
Set stream = field.GetStream(1, LCSTREAMFMT_NATIVE)...then perform your insert/update as you normally would.
This was first published in June 2002