Are there any free videos of moving psychedelic backgrounds for iMovie?

I've found a bunch of songs from my old basement band in 1979 that I would like to upload to Rumble, but I've already used up all of the old photos of us in the first video I made. So, I'd like to make a couple more videos of our songs, but have NOTHING to put in the video content. I can compose an intro explaining the song, but beyond that I have nothing to add to the video to make it visually interesting. The song I have now is 6:00 minutes long. I would love to add just a simple living/breathing psychedelic background just for visuals, but don't know how to go about this. I don't want to spend a ton of time on this. Any idea where one can get a long, free video sample to add to videos?