Try Super Strange Video. Their URL is http://www.superstrangevideo.com/index.asp.
Another one that jumps to the forefront of my mind is http://serial-bowl.com/index.html.
I'm gonna try that one, myself... The former has the other ones I'm looking for...
I've just started watching this serial colorized on You Tube. There are no signs of where one chapter begins and another ends. Even though it's done in full feature style I'm still going to watch it in chapter-style pieces and guess which ones were used for the cliff-hanger scenes.
It has just a bit of a misleading title as it implies alien invaders from space. But no. Rocket-launching sites are being planned and prepared by some foreign power. I'm going going to catch up on some of the earlier Republic serials sometime.