Seems to me like I saw them during the garden festival at Epcot. They had stuff for sale in one of the FW buildings...you kind of had to look for it. They also had booths around and someom may have had them.
At other times, I have seen that sort of thing on sale in Epcot near the American area in WS. It might have been during F &W festival. The booths look like a craft fair. I don't specifially recall flags, but I wasn't looking.