I see what you mean now.

You might just need to search for some free stock footage. I've got a couple of MOV files (1mb and 11mb) that have rolling clouds I could send you if you want. One's pretty short but you could time stretch it a bit. I've just tried it and it works fine. These kind of templates tend to come on cover mounts on magazines or freebies on some websites. You just need to search around I'm afraid.