There is another thread on here that discusses a workaround.
Well… the familiar php workaround when a function does not provide a “get to variable” output actually… use ob_start: http://php.net/manual/en/function.ob-start.php
to just capture the output and manipulate it before sending it on its way.
Leads on stackoverflow: https://stackoverflow.com/search?q=%2Bwordpress+sidebar+%2Bob-start+