Too much work man.. Just download some1 else spawn map-ready-media
But I'll tell you how anyways, but not the exact way :P
1. Extracts the map files (much files)
2. Convert the map files from ddj to dds (something like this, not exactly remember)
3. Edit the dds map files, add the little spot to the map.
4. Reconvert to ddj
5. Replace the current file in the media
Like I said, too much work..