ADV Films has released two DVDs of the series in the US; A Hero is Born contains season 1, while Battle for the Future is season 2 and that one episode people say is from a discontinued season 3 but I think they're just talking crazy talk. The two sets have leapt in price significantly over the years, and those that have it haven't even been cool enough to torrent it or anything, so YouTube is probably your best bet for watching it if you don't want to lose an arm and a leg.
Fun fact! The box art you see everywhere for A Hero Is Born (and here too due to laziness) is actually the art used on the disc!
Amazon US: A Hero Is Born | Battle for the Future
Amazon UK: A Hero Is Born | Battle for the Future