Oddly enough I've had such a thing kicking around for a while, so I went ahead and uploaded it. seed=<random seed>; constant=true for the behavior seed used to have.
http://foxyshadis.slightlydark.com/random/AddGrainC.zip
I definitely agree that encoding the output with xvid or quenc is the way to go. For simulating dot crawl/rainbowing, try analog capturing a good sequence. (Even as simple as wiring a cable from one computers's output card to another's input.)