Hello @j_wilkie
Thanks for posting this in the Global Canvas Community.
It looks like the attendance reports that can be run do not include the students SIS Id's. Reports will always include data fields for: Course ID, SIS Course ID, Course Code, Course Name, Teacher ID, Teacher Name, Student ID, Student Name, Class Date, Attendance, and Timestamp. This appears to be a limitation of the reports that can be run in Canvas. However, I do see how this would be helpful. My guess is that the report does not use the students SIS ID's to generate the report. Instead it pulls other bits of information.
This would make a great feature request for future releases in Canvas. I did not see any ideas had been submitted that were related this yet.
If you truly need to get the student sis id's, you could always run a Class Roster report in new analytics. Keep in mind, Report data may be delayed by 24 hours. This should export a report that displays the Student Name, Student SIS ID, Email, and Section Name. There is also a permissions that can be enabled by your school's admins on the account level that allows teachers to view SIS ID's for students from the People page. That permission is called SIS Data-Read and can be enabled on the course role level.
Hopefully this helps!
-Colton