I too have been on something of a Flash Gordon kick lately.
Right now my focus has been the Filmation adaptation, both the "made for TV" movie and the Saturday morning "serial" it spawned (but oddly enough aired some 2 years before the original movie cut).
However, a couple of years ago, I was in Best Buy and saw a 3 disk set that contained the first three serials (not episodes, but full serials) that starred Buster Crabbe in the titular role. So far I've only seen the first serial. The box set got "buried" under some junk and you know how it goes, "out of sight, out of mind."
Yesterday, I finally got to see the tele-movie cut of the Filmation material for the first time in, well, dang, 31 years! By the end of the week I should receive the box set containing all the Saturday morning episodes. (I won't bother watching the second season that introduced a cute mascot character in the form of a pink dragon hatchling. "Thank you, executive meddling!")