Getting LMS Username into Customized Quiz Report

We need to provide users with custom printouts of their quiz results. That is easy enough to accomplish by setting the result slide to "allow user to print results". This creates a REPORT.HTML in the output with can then be easily customized to include the question feedback. However, I cannot figure out how to get their LMS username into the report. (I need the formal username, not the available "prompt the user for their name before printing" feature.)

I have the username in a Storyline variable, via a JavaScript trigger on the first slide. Unfortunately, I can't seem to get this variable value into the HTML page using the Storyline GetPlayer (and GetVar) functions. I can't get either function to resolve from REPORT.HTML. Any suggestions?