Several graphics editors and converters support JPEG 2000 format (.jpx) and allow users to transform standard .jpg files to it.
However, this will have no real effect in most effects and the original JPEG file is heavily compressed with a data loss. To produce best JPEG 2000 images, you would have to make them from digital RAW photographs. No utility designed just for jpeg to jpx conversion will be of use unless you have access to the original picture in original quality.