The report has more columns than I mentioned and is already written using the Configurable Reports block. I've never written a report in PHP, although I'm not opposed to learning. But since the report is already written, I was hoping to just add a link to admin/users.php for the sake of the users' convenience.
Thanks for that bit of code. If I end up going the route of writing a new report, it will come in handy!
Kimber