Got mine at radio shack. It was cheap (under $20 USD). Has RCA for stereo L&R and composite for inputs and a regular RG6 RF plug on the output.

Oh and the RF distribution amp was less that $100 USD. Also from radio shack. The ones I use have 8 or so outputs each

It's funk though. Don't adjust the aspect ratio on your output. Your video monitor will be wide but it will look right on the TVs.

I've done this a zillion times in nightclubs.