I didn't read your thread all the way so I don't know if someone already suggested this but if you're looking for a Sgt. Stone, try Rite-Aid. They still have a few ROC action figures and not the typical Baroness/Destro/Neo-Viper pegwarmers. I'm sure I've seen a Stone at one 'round here in the last few months.
Of course, Rite-Aid charges $10.99 or so for them. Not sure if it'd be cheaper to get a Stone off ebay. He was never as common as a lot of the other ROC action figures 'round here.