Re: easily accessible videos of Internal Training in Aikido?
The trouble with internal training is that it is, in fact, internal. Anything you can see on a video is not what you're working for.
You can see videos of the various tests--O-Sensei popping someone off a knee or shoulder, people pushing on his head and unable to push him over--but that's the demonstration, not the training.
I don't want to comment on what Endo Sensei is doing, but what he is describing in the subtitles is not internals.