TRU has the MOTUC vs DC 2-packs, Auqaman vs Mer-Man and Hawkman vs Stratos. They can also be found in comic stores and places like that. But from what I've found here is that they charge anywhere from $60-$90 for one.. which is the most outrageous thing ive ever seen.
If you want to get older ones go to the He-man.org forums and people there are usually selling them for just a tab above cost. Otherwise mattycollector.com is the best and only place to get them for what they are being sold for.