A few weeks ago I picked up a S-Video/Analog switch box at Circuit City.
The device has 4 S-Video/Analog Video and Audio inputs. It also has two S-Video outputs. The device also contains an RF Modulator. The RF Modulator lets you send combined audio/video direct to your TV via a Standard TV coaxial RF output to input
It’s called a Terk Video Switch (MOD-41), and you can check it out here:
4-input RF modulator: Connects up to four A/V source inputs to your coaxial RF input, upgrading older TVs for use with DVD, PVR, VCR, camcorders and video game systems.
Compatible with: Most TVs, including ones with only coaxial RF inputs.
and it sells for: $34.99
It was exactly what I needed and may be what you are looking for.