How to make scroll bar visible at all times?

I was able to insert the following JS to create a scrolling list of answer choices on my multiple choice question:

Qualtrics.SurveyEngine.addOnReady(function()
{
jQuery("#"+this.questionId+" .QuestionBody").css({"overflow-y":"scroll","height":"615px"});
});

However, the scroll bar is not visible until the participant mouses over the answer choices and tries to begin scrolling, making it a bit unclear that this is even a scrolling list. Is there a way to insert some additional code to make the scroll bar visible at all times?