The Zip file containing the MotS secret level is actually located on the CD itself. ; )
You just need to modify the jkl (IIRC) file yourself in notepad and re-add it to the archive (goo file) using Conman or whatever or else you need to download the modified one from LucasArts (if the link is still active).
Otherwise you can probably find a modified version on the 'net for you to download and use.
And yeah, there's no secret level for JK.