Amazon has the Karaoke USA Portable System (Black, GF839) for $56 with free shipping. Features 35W peak digital power amplifier (25W RMS), record voice and music mix and instant playback, 300 MP3G songs.
Has good Amazon Reviews.
eBay has the Microphone Scissor Arm Suspension Boom for $9.99 with free shipping. Retail price: $30. Features adjustable legs for placement on uneven surfaces, compact microphone stand designed for heavy duty carry.