Build it yourself. I built one last year.
Jumbo coffe mug from Citgo= $5.00
Misc. cables/adapters from Radio Shack= $10.00
Speco 5" speaker= $14.00
Rio MP3 Player (new)= $65.00
Azden Wireless Microphone Sys.= $100.00
You cut the bottom out of the coffee mug, and secure the speaker with adhesive of your choice, I used RTV (silicone). Now take the top off, wire everything up, put lid back on. Download sounds to your computer, then move them to your MP3 player and you're ready to go.
I've simplified the instructions, but that is basically all there is to it. There are better instructions over at
www.predatormastersforums.com. Good luck.