Would it be allowed to use music from sites like http://www.elixic.de/index.php?id=industrial for your map ? Or music from the demoscene ? http://www.scene.org It's free music after all and the url could go into the credits. Or do i need the permission of the artists first ?
A friend of mine makes electronic/techno(or whatever it's called these days)music, and he used to be a part of a group of DJ's at this site: http://sickmode.org/ There's a shitload of mp3's over there, and the mp3's are mostly in a full song set-up, rather than tracks made that can be ran in a loop. If you wanted to see if you can get one of them to make a looping track, you should try bothering one of them. Not all of it's good, but some of it is really hypnotic or tripped-out.
My friends site is: http://grindthieves.com/artbreaker/ . He doesn't seem to have his mp3 links working at the moment(he just released a huge album so I dunno), but I like his stuff better than the good majority of stuff over there.
If you don't want to mess around with any of that amount of work....than I guess, check out some new music.