Video outputs are usually low impedance so you could try a 50 or 75 ohms in-line attenuator. Either impedance would do. Attenuators with RCA connections are probably unavailable, but they are available with BNC connectors and sometimes F-connectors. If you could find some you could use adapters at each end to get to and from the RCA cables.
For me in the electronics industry they are easily available, sometimes in surplus electronic stores, but it could be hard for you. If you could find some, you could start with 2 dB or 3 dB. They are additive so 2 + 3 does equal five. The attenuators could be in the $10 range each.
Alternatively, Mitsubishi owners are making their own attenuators out of Radio Shack parts (go to HDTV spot and search for fixing red push in Mitsubishi sets.)
If you are looking for really cheap, you said that a 75 ohm parallel resitor was too much. Why not try a larger value, say 150 ohms and keep moving up until you find the right value.
[This message has been edited by waters (edited 08-22-2001).]