I always just make my own.
You can pick up the stuff to make them for under $50 bucks at Radio Shack. You can even pick up a cheap kit to make it wireless. I just use my MP3 player as a source.
I found a cheeper way then the Radio shack el-cheepo this hooks into your mp3 player and has 75 foot of wire for 20$ Cabela's -- Cass Creek Bighorn Speaker
You can get a cheap Nady wireless guitar system to use for a remote. They say they're good to 250' or so, but I never tried that far. The receiver takes a little creative electrical work to power it with a battery. I've gotten to the point that I just edit my MP3s so that I have a couple minutes of silence at the beginning of the track to get situated, and set it to play just one track. If my track is 20-ish minutes it works fine.