You can get some amplified speakers at Radio Shack. They can run off of batteries or AC. They can hook up to a cdplayer via mini jack. Or you can run 12 gauge speaker wire to a homemade amp connected to a 1000 watt subwoofer and get some real power out of it. You would probably want to use a car battery for that though
Unless you want to be tethered by AC. You will need amplified speakers, discmans dont put out enough power to go loud enough.
The best way would just be get a mini boombox that can run off a bunch of batteries.