Width of sidebar

I have the free Make theme and am trying to figure out how to make the right sidebar slightly wider. I have an embedded audio player that’s specific to my business (I’m a voice actor, and this particular player is kind of industry standard) that can’t be adjusted for width. So I need to adjust the sidebar to fit it, because it cuts off some of the player.

I can’t seem to find the correct place to do this…can someone help please? It’s urgent, as my audio demos need to be the first thing clients see and click, so I need it to look correct. Thanks!