Okay, here's the info I was able to find. The file name is nightclub.zip (462 Kb) and it's by FlyDuDe (FlyGuyRy69@aol.com might no longer work). It apparently was released 8/15/99.
I just haven't had time to check through all my old cd-roms to find it though, admittedly.
Three sites list the file for download (but have broken links). Not sure if you could try contacting the webmasters (if they are not long vanished):
http://www.nightfaller.hpg.ig.com.br/jk.htm
http://theblackmesa.ifrance.com/levelsmulti.htm
http://members.yline.com/~garfield/jklevel.htm
I wonder if it was ever crammed into one of those Level packs out there? (edit: it's not part of Massassi Level Packs 1-4, or the Ultimate Guns Pack or Ultimate Saber Packs at JKMAG...)
The search continues...!