Generic ones are available at places like IconArchive and DeviantArt (which has a lot of NSFW content, but not drive related) companies that sell drives often make downloadable icons available of all the models they sell, like One World Computing and LaCie and you can copy an icon from an existing volume. You can find the source icons all over the place. But it’s a multi-step process that requires starting with the right image.
For many years-at least 15, by my research-you have been able to select and change the icon for any file, folder, volume, or drive. Apple hides some of its best features through obscurity, not intentionally.
