It may be slightly below your threshold for down fill (and slightly over for weight), but the Rab Neutrino Plus is a pretty fantastic winter/light expedition parka with 275g of down and about 750g total weight. Compared to the Feathered Friends models with decent groin/butt coverage (Frontpoint, Icefall, Rock & Ice), it's lighter and more compressible. The other Feathered Friends models are all pretty short, and barely reach the hip.
The SnoJack is a rather serious expedition parka and is amazingly lofty, but it's comparable to the Icefall in weight. My size large SnoJack weighs about 33 oz.
Otherwise, you could try to snag a Patagonia Encapsil belay parka on Ebay! (just kidding, of course)