I have found that frozen dumplings are a rarity in Qatar and thus whenever I see them I buy all they have in stock... usually it's only a few boxes. I've been most successful in the dumpling quest at Megamart where I got these Ling Ling potstickers. I have had them before in the US. They are not bad!
I've also been trying all the dumplings in the restaurants but have yet to find some that are really, really good. The dumplings at Sakura in the Ramada are pretty good.