Width of scroll bar in combo box

I’m designing a touchscreen UI, and I need to make the width of the scroll bar in the combo box component wider. I’d also like to make the arrow image on the right side of the text box wider, but the most important thing is the scroll bar width. Fat fingers have trouble scrolling easily because of the small target.

Anyone know if this can be done? And if not, anyone know of a third party component that has this configurability?

FYI, I’m using Flash 8.